Redesign phase A: SQLite storage, per-frame data model, device identity

Replaces the single global config.json (whole-file pydantic model under
one RLock) with SQLite via SQLAlchemy 2.0: users/sessions/frames/links/
pending-claims/battery_log tables (models.py), a per-frame lock registry
(db.frame_locked) succeeding config.locked(), and hand-rolled schema
versioning (migration.py). A pre-database deployment's config.json is
imported verbatim as frame #1 on first boot and left untouched as the
rollback path; the old single firmware.bin slot becomes per-frame
firmware/<id>.bin.

Routes split out of the 900-line main.py into routers/device.py (the
frozen /frame/* protocol) and routers/api.py (web UI, still on the old
single-frame paths for now). Device auth moves to require_device, which
already speaks the full multi-frame protocol: per-frame device tokens
pushed via /frame/config and acknowledged on first use, self-
registration of unknown device ids as unclaimed frames, pending-claim
attachment, and the legacy-token migration window that keeps the
currently-deployed firmware (no id, shared MANAGEMENT_TOKEN) resolving
to frame #1 -- including the one-time binding of its device id when it
first reports one after a future OTA.

Externally identical for existing deployments: same paths, same token
semantics, same response shapes -- verified with a migration fixture,
the legacy-device curl suite, a 20-way concurrent-advance smoke test,
and a mutate-restart-assert persistence check against a fake Immich.

photo_queue.py ports nearly verbatim onto the Frame ORM row (MutableList
JSON columns make its in-place list mutations dirty-track); quiet-hours
math extracted unchanged into quiet_hours.py.

server/app/firmware.py

@@ -1,7 +1,8 @@
-"""Local firmware image storage + esp_app_desc_t parsing. Shared by the
-manual upload path (POST /api/firmware) and the Gitea auto-update path
-(see gitea_releases.py) -- both end up writing the same firmware.bin slot
-that GET /frame/firmware streams to the device."""
+"""Per-frame firmware image storage + esp_app_desc_t parsing. Shared by
+the manual upload path and the Gitea auto-update path -- both end up
+writing the same per-frame slot that GET /frame/firmware streams to the
+device. The migration moves the old single /data/firmware.bin into frame
+#1's slot."""
 
 from __future__ import annotations
 
@@ -18,8 +19,8 @@ APP_DESC_MAGIC = 0xABCD5432
 EXPECTED_PROJECT_NAME = "espresso_frame"
 
 
-def firmware_path():
-    return config.CONFIG_PATH.parent / "firmware.bin"
+def firmware_path(frame_id: int):
+    return config.CONFIG_PATH.parent / "firmware" / f"{frame_id}.bin"
 
 
 def parse_app_version(data: bytes) -> str: