serve: add JWT consumer shim for bincio-auth integration

When --jwt-secret / BINCIO_AUTH_JWT_SECRET is set, auth is validated
locally by decoding the bincio-auth-issued JWT — no DB session lookup.
Falls back to existing DB-based session lookup when the flag is absent,
so standalone deployments keep working without any config change.

Changes:
- deps.py: add jwt_secret global, _decode_jwt helper, wire into
  _current_user and _require_auth
- cli.py: add --jwt-secret option; log active auth mode on startup
- pyproject.toml: add PyJWT>=2.8 to serve and dev extras

bincio/serve/cli.py

@@ -3,7 +3,6 @@
 from __future__ import annotations
 
 from pathlib import Path
-from typing import Optional
 
 import click
 from rich.console import Console
@@ -23,11 +22,12 @@ console = Console()
 @click.option("--webroot", default=None, type=click.Path(), help="Nginx webroot (e.g. /var/www/bincio). When set, uploads trigger a full Astro build + rsync so new activity pages are immediately accessible without a git push.")
 @click.option("--dem-url", default=None, envvar="DEM_URL", help="Base URL of an Open-Elevation-compatible API (default: https://api.open-elevation.com).")
 @click.option("--sync-secret", default=None, envvar="BINCIO_SYNC_SECRET", help="Shared secret for POST /api/internal/rebuild (used by the sync-strava systemd timer).")
-def serve(data_dir: str, site_dir: Optional[str], host: str, port: int,
-          strava_client_id: Optional[str], strava_client_secret: Optional[str],
-          max_users: Optional[int], public_url: Optional[str],
-          webroot: Optional[str], dem_url: Optional[str],
-          sync_secret: Optional[str]) -> None:
+@click.option("--jwt-secret", default=None, envvar="BINCIO_AUTH_JWT_SECRET", help="Shared JWT secret from bincio-auth. When set, validates JWTs locally instead of DB session lookup.")
+def serve(data_dir: str, site_dir: str | None, host: str, port: int,
+          strava_client_id: str | None, strava_client_secret: str | None,
+          max_users: int | None, public_url: str | None,
+          webroot: str | None, dem_url: str | None,
+          sync_secret: str | None, jwt_secret: str | None) -> None:
     """Start the bincio multi-user application server.
 
     Handles auth, user management, and write operations.
@@ -36,9 +36,10 @@ def serve(data_dir: str, site_dir: Optional[str], host: str, port: int,
     Requires a data directory initialised with `bincio init`.
     """
     import uvicorn
+
     import bincio.serve.server as srv
     from bincio.serve import deps
-    from bincio.serve.db import open_db, set_setting, get_setting
+    from bincio.serve.db import get_setting, open_db, set_setting
 
     dd = Path(data_dir).expanduser().resolve()
     if not (dd / "instance.db").exists():
@@ -66,12 +67,14 @@ def serve(data_dir: str, site_dir: Optional[str], host: str, port: int,
         deps.dem_url = dem_url
     if sync_secret:
         deps.sync_secret = sync_secret
+    if jwt_secret:
+        deps.jwt_secret = jwt_secret
 
     db = open_db(dd)
     current_limit = get_setting(db, "max_users")
     db.close()
 
-    console.print(f"[bold]bincio serve[/bold]")
+    console.print("[bold]bincio serve[/bold]")
     console.print(f"  Data:  [cyan]{dd}[/cyan]")
     if deps.site_dir:
         console.print(f"  Site:  [cyan]{deps.site_dir}[/cyan]")
@@ -81,8 +84,12 @@ def serve(data_dir: str, site_dir: Optional[str], host: str, port: int,
     if current_limit and int(current_limit) > 0:
         console.print(f"  Users: [yellow]max {current_limit}[/yellow]")
     else:
-        console.print(f"  Users: [dim]unlimited[/dim]")
+        console.print("  Users: [dim]unlimited[/dim]")
     console.print(f"  DEM:   [cyan]{deps.dem_url}[/cyan]")
+    if deps.jwt_secret:
+        console.print("  Auth:  [green]JWT (bincio-auth)[/green]")
+    else:
+        console.print("  Auth:  [dim]local DB sessions[/dim]")
     console.print()
 
     log_config = uvicorn.config.LOGGING_CONFIG.copy()

bincio/serve/deps.py

@@ -12,20 +12,16 @@ import re
 import threading
 import time
 from pathlib import Path
-from typing import Optional
 
+import jwt as _jwt
 from fastapi import Cookie, HTTPException, Request, Response
 
+from bincio.edit.ops import VALID_ACTIVITY_ID as _VALID_ACTIVITY_ID
 from bincio.serve.db import (
     User,
-    authenticate,
-    create_session,
-    delete_session,
     get_session,
-    get_user,
     open_db,
 )
-from bincio.edit.ops import VALID_ACTIVITY_ID as _VALID_ACTIVITY_ID
 from bincio.shared.images import ALLOWED_IMAGE_TYPES as _ALLOWED_IMAGE_TYPES  # noqa: F401
 from bincio.shared.images import MAX_IMAGE_BYTES as _MAX_IMAGE_BYTES  # noqa: F401
 from bincio.shared.images import unique_image_name as _unique_image_name  # noqa: F401
@@ -40,6 +36,7 @@ strava_client_secret: str = ""
 public_url: str = ""
 dem_url: str = "https://api.open-elevation.com"
 sync_secret: str = ""
+jwt_secret: str = ""  # when set, validates JWTs from bincio-auth instead of DB session lookup
 _db = None
 _strava_sync_running = False
 _strava_sync_lock = threading.Lock()
@@ -118,20 +115,42 @@ def _check_rate_limit(
 
 # ── Auth dependency functions ─────────────────────────────────────────────────
 
-def _current_user(bincio_session: Optional[str] = Cookie(default=None)) -> Optional[User]:
+def _decode_jwt(token: str) -> User | None:
+    """Decode a bincio-auth JWT and return a User. Returns None on any failure."""
+    try:
+        payload = _jwt.decode(token, jwt_secret, algorithms=["HS256"])
+    except _jwt.PyJWTError:
+        return None
+    handle = payload.get("sub")
+    if not handle:
+        return None
+    return User(
+        handle=handle,
+        display_name=payload.get("display_name", ""),
+        is_admin=bool(payload.get("is_admin", False)),
+        wiki_access=bool(payload.get("wiki_access", True)),
+        activity_access=bool(payload.get("activity_access", False)),
+        suspended=False,
+        created_at=0,
+    )
+
+
+def _current_user(bincio_session: str | None = Cookie(default=None)) -> User | None:
     if not bincio_session:
         return None
+    if jwt_secret:
+        return _decode_jwt(bincio_session)
     return get_session(_get_db(), bincio_session)
 
 
-def _require_user(bincio_session: Optional[str] = Cookie(default=None)) -> User:
+def _require_user(bincio_session: str | None = Cookie(default=None)) -> User:
     user = _current_user(bincio_session)
     if not user:
         raise HTTPException(401, "Not authenticated")
     return user
 
 
-def _require_admin(bincio_session: Optional[str] = Cookie(default=None)) -> User:
+def _require_admin(bincio_session: str | None = Cookie(default=None)) -> User:
     user = _require_user(bincio_session)
     if not user.is_admin:
         raise HTTPException(403, "Admin required")
@@ -140,7 +159,7 @@ def _require_admin(bincio_session: Optional[str] = Cookie(default=None)) -> User
 
 def _require_auth(
     request: Request,
-    bincio_session: Optional[str] = Cookie(default=None),
+    bincio_session: str | None = Cookie(default=None),
 ) -> User:
     """Accept session cookie (web) OR Authorization: Bearer token (mobile)."""
     token = bincio_session
@@ -150,7 +169,7 @@ def _require_auth(
             token = auth[7:]
     if not token:
         raise HTTPException(401, "Not authenticated")
-    user = get_session(_get_db(), token)
+    user = _decode_jwt(token) if jwt_secret else get_session(_get_db(), token)
     if not user:
         raise HTTPException(401, "Invalid or expired session")
     return user

pyproject.toml

@@ -42,6 +42,7 @@ serve = [
     "uvicorn[standard]>=0.29",
     "python-multipart>=0.0.9",
     "bcrypt>=4.1",
+    "PyJWT>=2.8",
 ]
 strava = [
     "requests>=2.32",
@@ -79,6 +80,7 @@ dev = [
     "uvicorn[standard]>=0.29",
     "python-multipart>=0.0.9",
     "bcrypt>=4.1",
+    "PyJWT>=2.8",
     "httpx>=0.28.1",
 ]