feat(0.30.0): colonnes personnalisables par espace + mapping étiquette ↔ colonne

- Table board_columns par espace (clé immuable, nom/couleur/
  ordre libres, étiquette mappée + alias, drapeau Focus) ;
  définitions semées paresseusement depuis les valeurs
  historiques — sans personnalisation, comportement identique.
- Service app/board_columns.py : résolution, mapping
  étiquette→colonne (alias compris, ex. kanban_a_faire de
  Flowdeck), colonnes Focus/Wallboard.
- Board, API, adoption, miroirs d'étiquettes, déplacements,
  capture, santé, focus, wall, dashboard branchés sur les
  colonnes de l'espace ; validations dynamiques dans models
  (move_issue, set_column_order) et rules.
- Administration → Colonnes : ajouter (avant Terminé),
  renommer, réordonner, mapper, supprimer avec migration des
  cartes vers une colonne choisie, réinitialiser ; bouton
  🧱 Colonnes sur le board ; journal d'audit.
- Backlog et Terminé : colonnes système non supprimables.
- 254 tests verts (7 nouveaux, palier 20) ; smoke réel contre
  le vrai Gitea : création, affichage au board, suppression.

app/board_columns.py

@@ -0,0 +1,136 @@
+"""Colonnes de board personnalisables par espace (0.30.0).
+
+Avant : six colonnes codées en dur (backlog, todo, in_progress,
+qa, review, done) et un mapping fixe colonne → étiquette
+``kanban:<colonne>``. Maintenant, chaque espace de travail
+définit ses colonnes : nom d'affichage, couleur, ordre,
+étiquette de forge mappée et alias reconnus. Les clés sont
+immuables (les données board_state les référencent) ; backlog
+et done restent des colonnes système (renommables, non
+supprimables) parce qu'elles portent une sémantique : défaut
+des cartes neuves, et état fermé des issues.
+
+Sans définition propre, un espace retombe sur les défauts
+historiques — comportement 0.24 strictement conservé.
+"""
+
+from __future__ import annotations
+
+from app import models
+
+DEFAULT_COLUMNS: list[dict] = [
+    {"key": "backlog", "name": "📥 Backlog", "color": "#6b7280",
+     "label": "", "aliases": "", "kind": "backlog", "in_focus": 0},
+    {"key": "todo", "name": "📋 À faire", "color": "#3b82f6",
+     "label": "kanban:todo", "aliases": "", "kind": "flow",
+     "in_focus": 0},
+    {"key": "in_progress", "name": "🚧 En cours", "color": "#f59e0b",
+     "label": "kanban:in_progress", "aliases": "", "kind": "flow",
+     "in_focus": 1},
+    {"key": "qa", "name": "🧪 QA", "color": "#06b6d4",
+     "label": "kanban:qa", "aliases": "", "kind": "flow",
+     "in_focus": 1},
+    {"key": "review", "name": "🔍 Révision", "color": "#8b5cf6",
+     "label": "kanban:review", "aliases": "", "kind": "flow",
+     "in_focus": 1},
+    {"key": "done", "name": "✅ Terminé", "color": "#10b981",
+     "label": "", "aliases": "", "kind": "done", "in_focus": 0},
+]
+
+_cache: dict[int, list[dict]] = {}
+
+
+def invalidate(workspace_id: int | None = None) -> None:
+    if workspace_id is None:
+        _cache.clear()
+    else:
+        _cache.pop(workspace_id, None)
+
+
+def ensure_columns(workspace_id: int) -> list[dict]:
+    """Seed the historical defaults if the workspace has none."""
+    existing = models.list_board_columns(workspace_id)
+    if existing:
+        return existing
+    for position, column in enumerate(DEFAULT_COLUMNS):
+        models.upsert_board_column(
+            workspace_id, {**column, "position": position}
+        )
+    invalidate(workspace_id)
+    return models.list_board_columns(workspace_id)
+
+
+def get_columns(workspace_id: int = 1) -> list[dict]:
+    """Effective columns of a workspace (cached, seeded lazily)."""
+    if workspace_id not in _cache:
+        _cache[workspace_id] = ensure_columns(workspace_id)
+    return _cache[workspace_id]
+
+
+def keys(workspace_id: int = 1) -> list[str]:
+    return [c["key"] for c in get_columns(workspace_id)]
+
+
+def names(workspace_id: int = 1) -> dict[str, str]:
+    return {c["key"]: c["name"] for c in get_columns(workspace_id)}
+
+
+def colors(workspace_id: int = 1) -> dict[str, str]:
+    return {c["key"]: c["color"] for c in get_columns(workspace_id)}
+
+
+def flow_keys(workspace_id: int = 1) -> list[str]:
+    return [
+        c["key"] for c in get_columns(workspace_id) if c["kind"] == "flow"
+    ]
+
+
+def focus_keys(workspace_id: int = 1) -> list[str]:
+    return [
+        c["key"] for c in get_columns(workspace_id) if c.get("in_focus")
+    ]
+
+
+def wall_keys(workspace_id: int = 1) -> list[str]:
+    """Wallboard cards: focus columns + the first flow column."""
+    columns = get_columns(workspace_id)
+    wanted = {c["key"] for c in columns if c.get("in_focus")}
+    flow = [c["key"] for c in columns if c["kind"] == "flow"]
+    if flow:
+        wanted.add(flow[0])
+    return [c["key"] for c in columns if c["key"] in wanted]
+
+
+def label_for(workspace_id: int, key: str) -> str | None:
+    """The forge label mirrored when a card enters this column."""
+    for column in get_columns(workspace_id):
+        if column["key"] == key and column["kind"] == "flow":
+            return column.get("label") or None
+    return None
+
+
+def label_lookup(workspace_id: int = 1) -> dict[str, str]:
+    """label name (lowercased) → column key, aliases included.
+
+    This is the configurable label/column mapping: the canonical
+    label of each flow column plus every alias declared for it
+    (e.g. Flowdeck's ``kanban_a_faire`` on the todo column).
+    """
+    lookup: dict[str, str] = {}
+    for column in get_columns(workspace_id):
+        if column["kind"] != "flow":
+            continue
+        names = [column.get("label") or ""]
+        names += [
+            a.strip() for a in (column.get("aliases") or "").split(",")
+        ]
+        for name in names:
+            name = name.strip().lower()
+            if name:
+                lookup[name] = column["key"]
+    return lookup
+
+
+def recognized_labels(workspace_id: int = 1) -> set[str]:
+    """Every label name (lowercased) owned by the mapping."""
+    return set(label_lookup(workspace_id))