feat: chat E2EE MVP - rooms list + timeline + composer + sync (issues 0148+0149+0150)

Backend extends MatrixService with Start()/Stop()/ListRooms()/LoadTimeline()/
SendText()/SendMarkdown(). On login the service initialises the crypto store
(cryptohelper, Olm/Megolm via goolm build tag) and a sync loop that fans
events out through Wails events ("matrix:event", "matrix:error"). Pickle
key is 32 random bytes hex-encoded in the OS keyring alongside the access
token, so the crypto SQLite store survives restarts.

Vendors 4 fresh helpers from fn_registry/functions/infra/:
  matrix_crypto_init.go (//go:build goolm || libolm)
  matrix_sync_service.go
  matrix_message_send.go
  matrix_room_list.go
Plus the existing 3 (mas_oidc_loopback, keyring_token_store, matrix_client_init).
go-sqlite3 driver pulled explicitly via sqlite_driver.go.

Frontend rewires HomeScreen as a 3-zone AppShell (sidebar / timeline /
composer). useMatrixRooms polls + reacts to the sync stream; useMatrixTimeline
loads the last 50 events of the selected room and appends live ones. New
components: RoomList, Timeline, EventBubble, Composer. Composer supports
plain text (default) and a markdown toggle; Enter sends, Shift+Enter newline.

wails.json now passes "build:tags": "goolm" by default. Tested with
wails build -tags goolm on linux/amd64 and windows/amd64.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

sqlite_driver.go

@@ -0,0 +1,15 @@
+package main
+
+// sqlite_driver.go registers the SQLite driver required by the mautrix crypto
+// store. mautrix-go's cryptohelper uses database/sql + the "sqlite3" driver
+// name. go-sqlite3 self-registers via init() with sync.Once internally, but we
+// keep the blank import here to make the dependency explicit.
+//
+// Per the project memory (feedback_agents_e2ee_unblock_pattern.md), if the
+// driver is somehow registered twice the panic shows up as
+// `sql: Register called twice for driver sqlite3`. The guard pattern lives in
+// go-sqlite3 itself, so a blank import is sufficient.
+
+import (
+	_ "github.com/mattn/go-sqlite3"
+)