M2-T11: serve React SPA from FastAPI and remove Jinja pages

- app/main.py serves the SPA build (SPA_DIST_DIR, default frontend/dist):
  mounts /assets and a GET catch-all returning index.html for client routes;
  catch-all 404s on /api/*, never swallows /docs, /openapi.json, /static, assets,
  ingestion/ticktick/status; skips SPA serving when dist absent (backend-only CI)
- delete app/api/routes/pages.py, app/api/routes/auth.py, app/templates/
  (all replaced by /api/* + SPA; auth service layer kept)
- remove/replace Jinja page tests (JSON coverage already in test_api_*);
  add tests/test_spa_hosting.py for the fallback contract
- regenerate openapi/ (Jinja paths gone) and frontend schema.d.ts

app/main.py

@@ -1,7 +1,10 @@
+import logging
+import os
 from contextlib import asynccontextmanager
 from pathlib import Path
 
-from fastapi import FastAPI
+from fastapi import FastAPI, HTTPException, Request
+from fastapi.responses import FileResponse
 from fastapi.staticfiles import StaticFiles
 from apscheduler.schedulers.background import BackgroundScheduler
 from apscheduler.triggers.interval import IntervalTrigger
@@ -11,8 +14,7 @@ from app import models  # noqa: F401
 from app.api.routes.api.config import router as api_config_router
 from app.api.routes.api.data import router as api_data_router
 from app.api.routes.api.session import router as api_session_router
-from app.api.routes.auth import router as auth_router
-from app.api.routes import pages, status
+from app.api.routes import status
 from app.db import get_session_local
 from app.api.routes.homeassistant import router as homeassistant_router
 from app.api.routes.location import router as location_router
@@ -25,6 +27,17 @@ from app.services.config_page import seed_missing_config_from_bootstrap, sync_ap
 from app.services.public_ip import check_public_ipv4_and_notify
 from scripts.app_db_adopt import AppDatabaseAdoptionError, validate_app_runtime_db
 
+logger = logging.getLogger(__name__)
+
+_REPO_ROOT = Path(__file__).resolve().parents[1]
+
+
+def _get_spa_dist_dir() -> Path:
+    env_val = os.environ.get("SPA_DIST_DIR")
+    if env_val:
+        return Path(env_val)
+    return _REPO_ROOT / "frontend" / "dist"
+
 
 def _run_scheduled_public_ip_check() -> None:
     session_local = get_session_local()
@@ -92,8 +105,6 @@ def create_app() -> FastAPI:
     app.mount("/static", StaticFiles(directory=static_dir), name="static")
 
     app.include_router(status.router)
-    app.include_router(auth_router)
-    app.include_router(pages.router)
     app.include_router(api_config_router)
     app.include_router(api_data_router)
     app.include_router(api_session_router)
@@ -102,6 +113,39 @@ def create_app() -> FastAPI:
     app.include_router(poo_router)
     app.include_router(public_ip_router)
     app.include_router(ticktick_router)
+
+    # SPA hosting: mount frontend/dist if it exists and has index.html.
+    # If the SPA dist is absent (e.g. backend-only CI), skip SPA serving entirely
+    # so that pytest stays green with only the API routes registered.
+    spa_dist = _get_spa_dist_dir()
+    spa_index = spa_dist / "index.html"
+    if spa_dist.is_dir() and spa_index.is_file():
+        spa_assets = spa_dist / "assets"
+        if spa_assets.is_dir():
+            app.mount("/assets", StaticFiles(directory=spa_assets), name="spa-assets")
+
+        # Resolve the dist root once so the containment check is fast and consistent.
+        _spa_root = spa_dist.resolve()
+
+        @app.get("/{full_path:path}", include_in_schema=False)
+        async def spa_fallback(full_path: str, request: Request) -> FileResponse:  # noqa: RUF029
+            # Explicit 404 for unmatched /api/* — never return index.html for API paths.
+            if full_path.startswith("api/"):
+                raise HTTPException(status_code=404, detail="not found")
+            # Resolve candidate to an absolute path and verify it stays within the SPA
+            # dist root.  Without this check, URL-encoded ".." sequences (e.g. "..%2f")
+            # bypass Starlette's path parameter handling and allow arbitrary file reads.
+            candidate = (spa_dist / full_path).resolve()
+            if candidate.is_file() and candidate.is_relative_to(_spa_root):
+                return FileResponse(candidate)
+            # For any path outside the dist root, or for SPA client routes that don't
+            # correspond to a real file, return index.html so the SPA router handles it.
+            return FileResponse(spa_index)
+    else:
+        logger.warning(
+            "SPA dist not found at %s — SPA hosting disabled (API-only mode).", spa_dist
+        )
+
     return app