feat(perf): chantier B — instantanés SQLite et rafraîchisseur d'arrière-plan

- Table snapshots + écriture traversante du cache client,
  hydratation au démarrage (SWR : servi + rafraîchi en fond).
- Boucle de rafraîchissement (120 s par défaut) : index, étoiles,
  issues all+open et jalons des projets actifs ; webhook =
  rafraîchissement immédiat du dépôt ; fraîcheur affichée.

app/gitea_client.py

@@ -64,6 +64,10 @@ class GiteaClient:
         self._cache: dict[str, tuple[float, Any]] = {}
         self._refreshing: set[str] = set()
         self._cache_gen = 0
+        # Snapshot bookkeeping (chantier B): cache key -> UTC time
+        # the payload was fetched from Gitea, for the freshness
+        # label and the persisted `snapshots` table.
+        self._snapshot_times: dict[str, str] = {}
 
     async def aclose(self) -> None:
         await self.client.aclose()
@@ -112,6 +116,90 @@ class GiteaClient:
     def _cache_put(self, key: str, value: Any) -> None:
         if self.cache_ttl > 0:
             self._cache[key] = (time.monotonic(), value)
+            self._persist_snapshot(key, value)
+
+    # ── Snapshots (chantier B, 0.22.0) ──────────────────────
+
+    def _persist_snapshot(self, key: str, value: Any) -> None:
+        """Write-through to the SQLite snapshots table.
+
+        Persistence must never break a read: any failure (DB
+        locked, unserializable payload) is logged and swallowed.
+        """
+        try:
+            from app import models
+
+            models.save_snapshot(key, value)
+            import datetime
+
+            self._snapshot_times[key] = datetime.datetime.now(
+                datetime.timezone.utc
+            ).strftime("%Y-%m-%d %H:%M:%S")
+        except Exception as exc:
+            logger.debug("snapshot persist failed for %s: %s", key, exc)
+
+    def hydrate_from_snapshots(self) -> int:
+        """Preload the cache from persisted snapshots (startup).
+
+        Entries are inserted with an already-stale timestamp: the
+        SWR layer serves them instantly AND schedules a background
+        refresh, so the first page after a restart renders from
+        local data (tens of ms) while Gitea data catches up.
+        Returns the number of entries hydrated.
+        """
+        if self.cache_ttl <= 0:
+            return 0
+        try:
+            from app import models
+
+            snapshots = models.load_snapshots()
+        except Exception as exc:
+            logger.warning("snapshot hydration failed: %s", exc)
+            return 0
+        stale_at = time.monotonic() - self.cache_ttl - 1.0
+        for key, (payload, updated_at) in snapshots.items():
+            self._cache[key] = (stale_at, payload)
+            self._snapshot_times[key] = updated_at
+        if snapshots:
+            logger.info("hydrated %d snapshot(s) from SQLite", len(snapshots))
+        return len(snapshots)
+
+    def latest_snapshot_at(self) -> str | None:
+        """Freshest Gitea fetch time across tracked keys (UTC str)."""
+        if not self._snapshot_times:
+            return None
+        return max(self._snapshot_times.values())
+
+    async def _force(self, key: str, fetcher: Callable[[], Awaitable[Any]]) -> Any:
+        """Fetch now, bypassing freshness (background refresher)."""
+        value = await fetcher()
+        self._cache_put(key, value)
+        return value
+
+    async def refresh_starred(self) -> list[dict]:
+        return await self._force(
+            "user:starred", lambda: self._get_all_pages("/user/starred")
+        )
+
+    async def refresh_repo_issues(
+        self, owner: str, repo: str, state: str = "all"
+    ) -> list[dict]:
+        return await self._force(
+            f"issues:{owner}/{repo}:{state}",
+            lambda: self._get_all_pages(
+                f"/repos/{owner}/{repo}/issues", state=state
+            ),
+        )
+
+    async def refresh_milestones(
+        self, owner: str, repo: str
+    ) -> list[dict]:
+        return await self._force(
+            f"milestones:{owner}/{repo}:open",
+            lambda: self._get_all_pages(
+                f"/repos/{owner}/{repo}/milestones", state="open"
+            ),
+        )
 
     def _cache_clear(self) -> None:
         self._cache.clear()
@@ -182,22 +270,25 @@ class GiteaClient:
             self._user = await self._get("/user")
         return self._user
 
+    async def _fetch_search_repos(self) -> list[dict]:
+        params: dict[str, Any] = {}
+        try:
+            user = await self.get_user()
+            if user and user.get("id"):
+                params["uid"] = user["id"]
+        except Exception as exc:  # no/invalid token → public search
+            logger.debug(
+                "get_user failed, falling back to public search: %s", exc
+            )
+        return await self._get_all_pages("/repos/search", **params)
+
     async def search_repos(self) -> list[dict]:
         """All repos visible to the token owner (paginated, SWR-cached)."""
+        return await self._cached_list("search_repos", self._fetch_search_repos)
 
-        async def _fetch() -> list[dict]:
-            params: dict[str, Any] = {}
-            try:
-                user = await self.get_user()
-                if user and user.get("id"):
-                    params["uid"] = user["id"]
-            except Exception as exc:  # no/invalid token → public search
-                logger.debug(
-                    "get_user failed, falling back to public search: %s", exc
-                )
-            return await self._get_all_pages("/repos/search", **params)
-
-        return await self._cached_list("search_repos", _fetch)
+    async def refresh_search_repos(self) -> list[dict]:
+        """Force-fetch the repo index (background refresher)."""
+        return await self._force("search_repos", self._fetch_search_repos)
 
     async def get_repo(self, owner: str, repo: str) -> dict:
         return await self._get(f"/repos/{owner}/{repo}")