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/photo_queue.py

@@ -34,12 +34,12 @@ from __future__ import annotations
 import random
 import time
 
-from .config import FrameConfig
+from .models import Frame
 
 HISTORY_MAX_LEN = 20
 
 
-def _top_up(cfg: FrameConfig, assets: list[dict]) -> None:
+def _top_up(cfg: Frame, assets: list[dict]) -> None:
     valid_ids = {a["id"] for a in assets}
     excluded_ids = set(cfg.excluded_asset_ids)
     cfg.queue = [asset_id for asset_id in cfg.queue if asset_id in valid_ids and asset_id not in excluded_ids]
@@ -85,7 +85,7 @@ def _top_up(cfg: FrameConfig, assets: list[dict]) -> None:
     cfg.queue_cursor = (cfg.queue_cursor + i + 1) % n
 
 
-def advance_forced(cfg: FrameConfig, assets: list[dict]) -> None:
+def advance_forced(cfg: Frame, assets: list[dict]) -> None:
     """Unconditionally moves to the next photo, ignoring elapsed time, and
     resets the interval clock from now. Used by the explicit next-photo
     action (POST /frame/advance) and by get_current() once the refresh
@@ -105,7 +105,7 @@ def advance_forced(cfg: FrameConfig, assets: list[dict]) -> None:
         # only asset is already current) -- keep showing what we have.
         cfg.current_asset_id = assets[0]["id"]
     cfg.current_asset_set_at = time.time()
-    cfg.stats.photos_displayed += 1
+    cfg.stats_photos_displayed += 1
     # Refill back up to queue_target_len now that current_asset_id has
     # changed -- otherwise the queue is left one short until the *next*
     # advance, since the pop above consumes one of the items _top_up just
@@ -113,7 +113,7 @@ def advance_forced(cfg: FrameConfig, assets: list[dict]) -> None:
     _top_up(cfg, assets)
 
 
-def back_forced(cfg: FrameConfig, assets: list[dict]) -> bool:
+def back_forced(cfg: Frame, assets: list[dict]) -> bool:
     """Unconditionally moves to the previously-current photo, the mirror
     image of advance_forced() -- pops the most recent entry off history,
     pushes the photo it's replacing onto the front of queue (so pressing
@@ -132,12 +132,12 @@ def back_forced(cfg: FrameConfig, assets: list[dict]) -> bool:
             cfg.queue.insert(0, cfg.current_asset_id)
         cfg.current_asset_id = previous_id
         cfg.current_asset_set_at = time.time()
-        cfg.stats.photos_displayed += 1
+        cfg.stats_photos_displayed += 1
         return True
     return False
 
 
-def remove_from_rotation(cfg: FrameConfig, assets: list[dict], asset_id: str) -> bool:
+def remove_from_rotation(cfg: Frame, assets: list[dict], asset_id: str) -> bool:
     """Permanently excludes asset_id from this frame's rotation (see the
     module docstring) -- doesn't touch Immich, just this frame's own
     selection. Scrubs it out of queue and history too, so it can't
@@ -149,7 +149,7 @@ def remove_from_rotation(cfg: FrameConfig, assets: list[dict], asset_id: str) ->
     changed as a result."""
     if asset_id not in cfg.excluded_asset_ids:
         cfg.excluded_asset_ids.append(asset_id)
-        cfg.stats.photos_removed += 1
+        cfg.stats_photos_removed += 1
     cfg.queue = [a for a in cfg.queue if a != asset_id]
     cfg.history = [a for a in cfg.history if a != asset_id]
 
@@ -167,12 +167,12 @@ def remove_from_rotation(cfg: FrameConfig, assets: list[dict], asset_id: str) ->
         remaining = [a["id"] for a in assets if a["id"] not in excluded_ids]
         cfg.current_asset_id = remaining[0] if remaining else ""
     cfg.current_asset_set_at = time.time()
-    cfg.stats.photos_displayed += 1
+    cfg.stats_photos_displayed += 1
     _top_up(cfg, assets)
     return True
 
 
-def sync_queue_length(cfg: FrameConfig, assets: list[dict]) -> None:
+def sync_queue_length(cfg: Frame, assets: list[dict]) -> None:
     """Tops up or trims cfg.queue to match cfg.queue_target_len without
     otherwise touching current_asset_id. Used by GET /api/queue so a
     change to the "upcoming photos to show" setting takes effect on page
@@ -180,7 +180,7 @@ def sync_queue_length(cfg: FrameConfig, assets: list[dict]) -> None:
     _top_up(cfg, assets)
 
 
-def get_current(cfg: FrameConfig, assets: list[dict], in_quiet_hours: bool = False) -> bool:
+def get_current(cfg: Frame, assets: list[dict], in_quiet_hours: bool = False) -> bool:
     """Time-based, idempotent path used by GET /frame/image. Advances only
     if the current photo is unset/invalid or refresh_interval_s has
     elapsed since it was set. Returns whether it changed anything, so the