feat(forecast): prévisions au débit réel du journal (issue #7)

app/forecast.py: fermetures hebdo (8 sem.), débit moy/min/max sur
4 semaines complètes, ETA en fourchette, silence sans historique.
Dashboard (épuisement du backlog), bandeau milestone (alerte
échéance), page /forecast (sparkline SVG, verdicts), /api/metrics
étendu (weekly_closures, throughput_4w).

app/forecast.py

@@ -0,0 +1,119 @@
+"""Forecasts (roadmap #7): honest ETAs from the event journal.
+
+Throughput = issues closed per week, counted from board_events.
+Projections are deliberately given as a RANGE (best/worst weekly
+rate over the last 4 complete weeks) rather than a fake-precise
+date, and are withheld entirely when the journal has no closures
+to learn from — "not enough history" is an answer, too.
+"""
+
+from datetime import date, datetime, timedelta
+
+MONTHS_FR = [
+    "janvier", "février", "mars", "avril", "mai", "juin",
+    "juillet", "août", "septembre", "octobre", "novembre", "décembre",
+]
+MONTHS_FR_SHORT = [
+    "janv.", "févr.", "mars", "avr.", "mai", "juin",
+    "juil.", "août", "sept.", "oct.", "nov.", "déc.",
+]
+
+
+def french_date(d: date, short: bool = False) -> str:
+    months = MONTHS_FR_SHORT if short else MONTHS_FR
+    return f"{d.day} {months[d.month - 1]}"
+
+
+def _event_date(event: dict) -> date | None:
+    raw = str(event.get("created_at") or "")
+    try:
+        return datetime.strptime(raw[:10], "%Y-%m-%d").date()
+    except ValueError:
+        return None
+
+
+def weekly_closures(events: list[dict], weeks: int = 8,
+                    today: date | None = None) -> list[dict]:
+    """Closure counts per ISO week, oldest first, current week last."""
+    today = today or date.today()
+    current_monday = today - timedelta(days=today.weekday())
+    buckets: list[dict] = []
+    for i in range(weeks - 1, -1, -1):
+        start = current_monday - timedelta(weeks=i)
+        buckets.append({"start": start, "count": 0})
+    by_start = {b["start"]: b for b in buckets}
+    for event in events:
+        if event.get("event_type") != "closed":
+            continue
+        day = _event_date(event)
+        if day is None:
+            continue
+        monday = day - timedelta(days=day.weekday())
+        if monday in by_start:
+            by_start[monday]["count"] += 1
+    return buckets
+
+
+def throughput_stats(weekly: list[dict], last: int = 4) -> dict | None:
+    """avg/min/max closures per week over the last COMPLETE weeks.
+
+    The current (partial) week is excluded: on Monday morning it
+    would crush the average for no reason. Returns None when the
+    complete weeks contain no closure at all.
+    """
+    complete = weekly[:-1][-last:] if len(weekly) > 1 else []
+    if not complete:
+        return None
+    counts = [b["count"] for b in complete]
+    if sum(counts) == 0:
+        return None
+    return {
+        "avg": sum(counts) / len(counts),
+        "min": min(counts),
+        "max": max(counts),
+        "weeks": len(counts),
+    }
+
+
+def estimate(remaining: int, weekly: list[dict],
+             today: date | None = None) -> dict | None:
+    """Projected completion for `remaining` items at the real pace.
+
+    Returns {"done": True} when nothing remains, None when there is
+    no throughput to project from, else dates: central (avg rate),
+    earliest (best week), latest (worst nonzero week, if any).
+    """
+    today = today or date.today()
+    if remaining <= 0:
+        return {"done": True}
+    stats = throughput_stats(weekly)
+    if stats is None:
+        return None
+
+    def at_rate(rate: float) -> date:
+        days = remaining / rate * 7
+        return today + timedelta(days=max(1, round(days)))
+
+    result = {
+        "done": False,
+        "avg_per_week": round(stats["avg"], 1),
+        "central": at_rate(stats["avg"]),
+        "earliest": at_rate(stats["max"]) if stats["max"] > 0 else None,
+        "latest": at_rate(stats["min"]) if stats["min"] > 0 else None,
+    }
+    return result
+
+
+def eta_label(est: dict | None, done_text: str = "terminé") -> str | None:
+    """One-line French label for banners and cards (or None)."""
+    if est is None:
+        return None
+    if est.get("done"):
+        return f"✅ {done_text}"
+    label = f"à ce rythme ≈ {french_date(est['central'], short=True)}"
+    if est.get("earliest") and est.get("latest"):
+        label += (
+            f" (fourchette {french_date(est['earliest'], short=True)}"
+            f" – {french_date(est['latest'], short=True)})"
+        )
+    return label

app/templates/dashboard.html

@@ -16,12 +16,14 @@
         <nav class="nav-pills">
             <a href="/" class="nav-pill active">🏠 Projets</a>
             <a href="/focus" class="nav-pill">🎯 Focus</a>
+            <a href="/today" class="nav-pill">🌅 Aujourd'hui</a>
             <a href="/my" class="nav-pill">👤 Mes issues</a>
             <a href="/activity" class="nav-pill">📰 Activité</a>
             <a href="/briefing" class="nav-pill">📊 Briefing</a>
             <a href="/search" class="nav-pill">🔍 Recherche</a>
             <a href="/capture" class="nav-pill">⚡ Capture</a>
             <a href="/digest" class="nav-pill">🧠 Digest</a>
+            <a href="/forecast" class="nav-pill">🔮 Prévisions</a>
             <a href="/wall" class="nav-pill">🖥️ Wallboard</a>
             <button type="button" class="nav-pill palette-trigger" title="Palette de commandes (Ctrl+K)">⌨️ Ctrl K</button>
         </nav>
@@ -86,6 +88,9 @@
                 {% endif %}
                 <div class="card-footer">
                     <span>{{ repo.open_issues_count or 0 }} issues ouvertes</span>
+                    {% if repo.forecast_label %}
+                    <span class="forecast-line" title="Prévision d'après le débit réel du journal (fermetures par semaine)">🔮 {{ repo.forecast_label }}</span>
+                    {% endif %}
                     {% if full in stats %}
                     <div class="mini-progress">
                         {% for col in ['backlog','todo','in_progress','qa','review','done'] %}

app/templates/forecast.html

@@ -0,0 +1,76 @@
+<!DOCTYPE html>
+<html lang="fr" data-theme="dark">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <meta name="csrf-token" content="{{ csrf_token }}">
+    <title>Prévisions — Kanbante</title>
+    <link rel="stylesheet" href="/static/css/style.css">
+</head>
+<body>
+    <header class="app-header">
+        <a href="/" class="logo">📋 Kanbante</a>
+        <nav class="nav-pills">
+            <a href="/" class="nav-pill">🏠 Projets</a>
+            <a href="/focus" class="nav-pill">🎯 Focus</a>
+            <a href="/today" class="nav-pill">🌅 Aujourd'hui</a>
+            <a href="/my" class="nav-pill">👤 Mes issues</a>
+            <a href="/activity" class="nav-pill">📰 Activité</a>
+            <a href="/briefing" class="nav-pill">📊 Briefing</a>
+            <a href="/search" class="nav-pill">🔍 Recherche</a>
+            <a href="/capture" class="nav-pill">⚡ Capture</a>
+            <a href="/digest" class="nav-pill">🧠 Digest</a>
+            <a href="/forecast" class="nav-pill active">🔮 Prévisions</a>
+            <a href="/wall" class="nav-pill">🖥️ Wallboard</a>
+            <button type="button" class="nav-pill palette-trigger" title="Palette de commandes (Ctrl+K)">⌨️ Ctrl K</button>
+        </nav>
+    </header>
+
+    <main class="focus-main">
+        <section class="briefing-card">
+            <h1>🔮 Prévisions — « on finit quand ? »</h1>
+            <p>Réponse honnête, calculée depuis le journal : fermetures réelles par semaine (8 dernières), débit moyen/min/max sur les 4 dernières semaines complètes, et fourchette plutôt que faux chiffre précis. Sans historique de fermetures, aucune prévision n'est affichée.</p>
+        </section>
+
+        {% for project in projects %}
+        <section class="briefing-card forecast-card">
+            <h2>📂 {{ project.full_name }}</h2>
+            <div class="forecast-flex">
+                <svg class="sparkline" viewBox="0 0 168 48" role="img" aria-label="Fermetures par semaine">
+                    {% for bar in project.bars %}
+                    {% set px = (bar.h * 0.42)|round|int %}
+                    <rect x="{{ loop.index0 * 21 }}" y="{{ 44 - px }}" width="15" height="{{ px if px > 0 else 1 }}" rx="2">
+                        <title>{{ bar.label }} : {{ bar.count }} fermée(s)</title>
+                    </rect>
+                    {% endfor %}
+                </svg>
+                <div class="forecast-nums">
+                    {% if project.stats %}
+                    <p>Débit : <strong>{{ project.stats.avg }} / semaine</strong> en moyenne (min {{ project.stats.min }}, max {{ project.stats.max }})</p>
+                    {% else %}
+                    <p>Débit : <strong>pas assez d'historique</strong> — aucune fermeture récente dans le journal.</p>
+                    {% endif %}
+                    <p>Restant ouvert : <strong>{{ project.remaining }}</strong>
+                    {% if project.eta_label %} · 🔮 backlog {{ project.eta_label }}{% endif %}</p>
+                </div>
+            </div>
+            {% if project.milestones %}
+            <ul class="forecast-milestones">
+                {% for ms in project.milestones %}
+                <li>🎯 <strong>{{ ms.title }}</strong> — {{ ms.remaining }} restante(s){% if ms.due_on %} · échéance {{ ms.due_on }}{% endif %}{% if ms.eta %} · 🔮 {{ ms.eta }}{% endif %}{% if ms.verdict %} · {{ ms.verdict }}{% endif %}</li>
+                {% endfor %}
+            </ul>
+            {% endif %}
+        </section>
+        {% else %}
+        <div class="briefing-card"><p>Aucun projet actif.</p></div>
+        {% endfor %}
+    </main>
+    <footer>
+        <span>Kanbante v{{ version }} · prévisions = journal des fermetures, pas boule de cristal</span>
+    </footer>
+    {% include "_palette.html" %}
+    <script src="/static/js/palette.js" defer></script>
+    <script src="/static/js/live.js" defer></script>
+</body>
+</html>