refactor(types): typed send helpers replace 16 as any casts (#210)

- sendRoomMessage (composer's fire-and-forget sends: text, location, voice,
  files, GIFs) and sendRoomEvent (polls, poll responses/ends, forwards,
  reactions, edits) in utils/room.ts carry the one cast each needs
  (`keyof TimelineEvents` / `RoomMessageEventContent`, no `any`).
- sendRoomMessage also swallows the rejected promise: a failed send already
  shows on the local echo (Failed to send + Retry, or the consent prompt), so
  it no longer surfaces as an unhandled error in the console.
- getAccountData narrows to `keyof AccountDataEvents`; ForwardMessageDialog's
  guard now narrows `contentToSend` itself (same behaviour).
- `as any` 39 → 23; eslint warnings 46 → 36, ratchet tightened to 36.

Verified in Chromium on a local Synapse: a text message, a quick reaction and
an edit all reach the server with the right content; a consent-blocked send
no longer logs an unhandled MatrixError. 1219 unit tests pass.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

package.json

@@ -12,7 +12,7 @@
     "build": "vite build",
     "preview": "vite preview",
     "lint": "npm run check:eslint && npm run check:prettier",
-    "check:eslint": "eslint src/* --max-warnings 46",
+    "check:eslint": "eslint src/* --max-warnings 36",
     "check:prettier": "prettier --check .",
     "fix:prettier": "prettier --write .",
     "typecheck": "tsc --noEmit",