feat(auth): share links open only their own widgets; unmarked routes are closed (#5033)

#5033 "Share links open only their own dashboard; every route without a
role is on an explicit allow-list". Any live share token in ?s= made the
caller a viewer on every viewer route — host pages, container logs, any
dashboard — and the host-agent widget routes had no role check at all.

- steward/dashboard/share.py: a share token opens, read-only, exactly the
  widget fragment URLs its own dashboard loads — same path, same
  configured parameters; only the time window (hours/range) may change.
- require_role marks its view; public_route marks the deliberately open
  ones (login, setup, health, the share page, agent ingest, install.sh,
  agent.py) with the reason. A before_request refuses any view with
  neither, so a route that forgets its decorator is closed, not open.
- /plugins/host_agent/widget and /widget/history now require viewer.
- The history widget's range buttons keep the rest of the query (and so
  a share link's token) instead of rebuilding it; the uptime widget's
  "Full SLA" link shows to logged-in users, not to share viewers.
- tests/test_route_access.py: a source scan that fails on any unmarked
  route in core or bundled plugins, the default-deny refusal, and the
  share matcher's cases.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

steward/app.py

@@ -137,6 +137,9 @@ def create_app(
     app.jinja_env.globals["csrf_token"] = _csrf.csrf_token
     app.jinja_env.globals["csrf_field"] = _csrf.csrf_field
     app.before_request(_csrf.check_request)
+    # Default-deny: a view with neither require_role nor public_route is refused.
+    from .auth.middleware import check_view_is_marked, public_route
+    app.before_request(check_view_is_marked)
 
     # ── 5. Plugin migrations ───────────────────────────────────────────────────
     # Step 3 already applied all plugin migrations via discover_all_plugin_migration_dirs,
@@ -233,33 +236,24 @@ def create_app(
     # ── 11. Share-token middleware ─────────────────────────────────────────────
     @app.before_request
     async def _validate_share_token():
-        """If ?s=<token> is present, validate it and set g.share_viewer."""
+        """A share link's token (?s=) opens, read-only, exactly the widget
+        fragments its own dashboard loads (steward/dashboard/share.py)."""
         from quart import request, g
         raw = request.args.get("s")
-        if not raw:
+        if not raw or request.method != "GET":
             return
         try:
-            import hashlib
-            from datetime import datetime, timezone
-            from sqlalchemy import select
-            from .models.dashboard import DashboardShareToken
-            token_hash = hashlib.sha256(raw.encode()).hexdigest()
+            from .dashboard.share import share_grants
             async with app.db_sessionmaker() as db:
-                result = await db.execute(
-                    select(DashboardShareToken)
-                    .where(DashboardShareToken.token_hash == token_hash)
-                )
-                share = result.scalar_one_or_none()
-            if share:
-                now = datetime.now(timezone.utc)
-                if share.expires_at is None or share.expires_at > now:
+                if await share_grants(db, raw, request.path, request.args):
                     g.share_viewer = True
-                    g.share_dashboard_id = share.dashboard_id
         except Exception:
-            pass  # never block a request due to token validation failure
+            # A failed check grants nothing; the request falls through to login.
+            logging.getLogger(__name__).exception("Share token check failed")
 
     # ── 11. Health check ───────────────────────────────────────────────────────
     @app.get("/health")
+    @public_route("liveness probe for the container")
     async def health():
         return {"status": "ok"}