feat!: remove the shared demo account

The demo account — one shared user that whitelisted emails entered from
the login page, reset on a schedule — goes end to end (owner decision,
E34): demo.py and the reset job, users.is_demo and demo_whitelist
(migration 0098 deletes the demo user, its audit rows, the reset job's
override and notices, then drops the column and table; the downgrade
restores the empty schema), the /auth/demo entry, the admin whitelist and
reset, the Demo tab, the banner, the login page's "Try the demo", and
every is_demo branch in routes, userscope, scheduler and the UI.

require_human only ever refused the demo account, so its 87 uses become
current_user (owner-approved); require_write_scope keeps its own check.
The login page's "or" divider now shows only beside the Google button:
without the demo entry under it, an instance without Google would have
said "or" to nothing.

A contract test (removedFeatures) fails on the word anywhere in the
backend, frontend, e2e or scripts — seen red on a planted hit. Size
ceilings tightened for the modules that shrank; admin.py is back under
the limit.

backend/app/routes/debug_sessions.py

@@ -2,8 +2,7 @@
 
 The session itself — what tags a request, its cap, its level — is `app/debugsession.py`. These routes
 are the user's handle on their OWN sessions only: another user's id 404s (`owned_or_404`), including
-for an admin, who reads everyone's lines in the diagnostics console instead. The shared demo account
-cannot record: its log would interleave every visitor under one account.
+for an admin, who reads everyone's lines in the diagnostics console instead.
 
 Screenshots arrive as a raw image body (`image/png`, `image/jpeg`, `image/webp`), not a multipart
 form — one image per request, capped while it arrives, and kept only if its bytes really are one of
@@ -21,7 +20,7 @@ from sqlalchemy.orm import Session
 
 from app import audit, debugsession, logs, logsink
 from app.audit import AuditAction
-from app.auth import require_human
+from app.auth import current_user
 from app.db import get_db, release_read_connection
 from app.issues import bundle, gitea
 from app.ratelimit import RateLimiter
@@ -51,7 +50,7 @@ _new_sessions = RateLimiter(max_events=20, window_seconds=3600)
 @router.post("")
 def start_session(
     body: StartIn,
-    user: User = Depends(require_human),
+    user: User = Depends(current_user),
     db: Session = Depends(get_db),
 ) -> dict:
     """Start recording, or join the recording already running (another tab started it)."""
@@ -79,7 +78,7 @@ def start_session(
 
 @router.post("/{sid}/stop")
 def stop_session(
-    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
+    sid: str, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> dict:
     session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
     if session.ended_at is None:
@@ -93,7 +92,7 @@ def stop_session(
 
 
 @router.get("")
-def list_sessions(user: User = Depends(require_human), db: Session = Depends(get_db)) -> dict:
+def list_sessions(user: User = Depends(current_user), db: Session = Depends(get_db)) -> dict:
     sessions = db.scalars(
         select(DebugSession)
         .where(DebugSession.user_id == user.id)
@@ -105,14 +104,14 @@ def list_sessions(user: User = Depends(require_human), db: Session = Depends(get
 
 @router.get("/{sid}")
 def get_session(
-    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
+    sid: str, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> dict:
     return _view(db, owned_or_404(db, DebugSession, sid, user, what="debug_session"))
 
 
 @router.get("/{sid}/events")
 def session_events(
-    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
+    sid: str, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> dict:
     """The rows an issue from this session would carry — browser and server, in time order."""
     session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
@@ -141,7 +140,7 @@ class DraftIn(BaseModel):
 def save_draft(
     sid: str,
     body: DraftIn,
-    user: User = Depends(require_human),
+    user: User = Depends(current_user),
     db: Session = Depends(get_db),
 ) -> dict:
     session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
@@ -162,7 +161,7 @@ def save_draft(
 
 @router.get("/{sid}/export")
 def export_session(
-    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
+    sid: str, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> Response:
     """The issue as a zip — the text, the two logs and the screenshots — for an instance without an
     issue tracker, or for sending it by hand. Built from the SAVED draft: what the composer shows is
@@ -208,9 +207,7 @@ def _issues_rate_limited() -> HTTPException:
 
 
 @router.post("/{sid}/issue")
-def send_issue(
-    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
-) -> dict:
+def send_issue(sid: str, user: User = Depends(current_user), db: Session = Depends(get_db)) -> dict:
     """Send the session's issue to the tracker — from the SAVED draft, as the export is built — or
     finish a send that stopped half-way (the issue exists; only what is missing is sent)."""
     session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
@@ -302,7 +299,7 @@ class PreviewIn(BaseModel):
 def preview_issue(
     sid: str,
     body: PreviewIn,
-    user: User = Depends(require_human),
+    user: User = Depends(current_user),
     db: Session = Depends(get_db),
 ) -> dict:
     """The body as the tracker will render it. Gitea sanitises its own output; the composer still
@@ -323,14 +320,14 @@ def _shot_view(shot: DebugScreenshot) -> dict:
 
 @router.get("/{sid}/screenshots")
 def list_screenshots(
-    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
+    sid: str, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> dict:
     session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
     return {"items": [_shot_view(s) for s in debugsession.screenshots(db, session)]}
 
 
 def _upload_target(
-    sid: str, user: User = Depends(require_human), db: Session = Depends(get_db)
+    sid: str, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> DebugSession:
     return owned_or_404(db, DebugSession, sid, user, what="debug_session")
 
@@ -393,7 +390,7 @@ def _screenshot_of(db: Session, session: DebugSession, shot_id: int) -> DebugScr
 
 @router.get("/{sid}/screenshots/{shot_id}")
 def get_screenshot(
-    sid: str, shot_id: int, user: User = Depends(require_human), db: Session = Depends(get_db)
+    sid: str, shot_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> Response:
     shot = _session_screenshot(db, sid, shot_id, user)
     # `nosniff`: the type was checked against the bytes at upload, and the browser must not guess.
@@ -406,7 +403,7 @@ def get_screenshot(
 
 @router.delete("/{sid}/screenshots/{shot_id}")
 def delete_screenshot(
-    sid: str, shot_id: int, user: User = Depends(require_human), db: Session = Depends(get_db)
+    sid: str, shot_id: int, user: User = Depends(current_user), db: Session = Depends(get_db)
 ) -> dict:
     session = owned_or_404(db, DebugSession, sid, user, what="debug_session")
     shot = _screenshot_of(db, session, shot_id)