fix(matrix): replace pickle crypto store with SQLite, fix E2EE decryption (#7981)

Fixes #7952 — Matrix E2EE completely broken after mautrix migration.

- Replace MemoryCryptoStore + pickle/HMAC persistence with mautrix's
  PgCryptoStore backed by SQLite via aiosqlite. Crypto state now
  persists reliably across restarts without fragile serialization.

- Add handle_sync() call on initial sync response so to-device events
  (queued Megolm key shares) are dispatched to OlmMachine instead of
  being silently dropped.

- Add _verify_device_keys_on_server() after loading crypto state.
  Detects missing keys (re-uploads), stale keys from migration
  (attempts re-upload), and corrupted state (refuses E2EE).

- Add _CryptoStateStore adapter wrapping MemoryStateStore to satisfy
  mautrix crypto's StateStore interface (is_encrypted,
  get_encryption_info, find_shared_rooms).

- Remove redundant share_keys() call from sync loop — OlmMachine
  already handles this via DEVICE_OTK_COUNT event handler.

- Fix datetime vs float TypeError in session.py suspend_recently_active()
  that crashed gateway startup.

- Add aiosqlite and asyncpg to [matrix] extra in pyproject.toml.

- Update test mocks for PgCryptoStore/Database and add query_keys mock
  for key verification. 174 tests pass.

- Add E2EE upgrade/migration docs to Matrix user guide.

pyproject.toml

@@ -43,7 +43,7 @@ dev = ["debugpy>=1.8.0,<2", "pytest>=9.0.2,<10", "pytest-asyncio>=1.3.0,<2", "py
 messaging = ["python-telegram-bot[webhooks]>=22.6,<23", "discord.py[voice]>=2.7.1,<3", "aiohttp>=3.13.3,<4", "slack-bolt>=1.18.0,<2", "slack-sdk>=3.27.0,<4"]
 cron = ["croniter>=6.0.0,<7"]
 slack = ["slack-bolt>=1.18.0,<2", "slack-sdk>=3.27.0,<4"]
-matrix = ["mautrix[encryption]>=0.20,<1", "Markdown>=3.6,<4"]
+matrix = ["mautrix[encryption]>=0.20,<1", "Markdown>=3.6,<4", "aiosqlite>=0.20", "asyncpg>=0.29"]
 cli = ["simple-term-menu>=1.0,<2"]
 tts-premium = ["elevenlabs>=1.0,<2"]
 voice = [