feat(v1.1.6): realtime channels + v1.1.5 follow-ups + version bumps

Server-side realtime SSE on per-app pub/sub topics, plus the three
v1.1.5 follow-ups and the version bumps.

Realtime:
- topics registry (0021) + admin endpoints + Capability::AppTopicManage
  (-> app:admin; no new scope).
- GET /realtime/topics/{topic} SSE endpoint (orchestrator-core data
  plane): Host -> app, RealtimeAuthority gate (404 missing/internal,
  401 bad/absent token), broadcast::Receiver stream + heartbeat.
- RealtimeBroadcaster / RealtimeEvent / RealtimeAuthority traits
  (picloud-shared); InProcessBroadcaster + GC (orchestrator-core);
  DB-backed RealtimeAuthorityImpl (manager-core). Publish path fans out
  to in-process subscribers after the durable outbox commit (best-effort,
  panic-isolated).
- HMAC subscriber tokens (subscriber_token.rs) + app_secrets table (0022)
  + pubsub::subscriber_token SDK (schema 1.6 -> 1.7). TTL clamp + env
  overrides.
- Dashboard Topics tab (register/list/edit/delete, prominent external
  badge, flip confirmation).

v1.1.5 follow-ups:
- Empty blobs accepted (NewFile/FileUpdate::validate) + round-trip test.
- Orphan *.tmp.* sweeper (spawn_files_orphan_sweep).
- Dispatcher e2e tests, one per trigger kind (DATABASE_URL-gated).

Versions: workspace 1.1.6, SDK 1.7, dashboard 0.12.0. Schema-snapshot
golden re-blessed.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -1,5 +1,91 @@
 # PiCloud Changelog
 
+## v1.1.6 — Realtime Channels & Client Library (unreleased)
+
+The first **external realtime surface** and the first **frontend
+library**, co-shipped per the §5/§6 design-notes decisions. Browser
+clients can subscribe over SSE to per-app pub/sub topics that have been
+explicitly externalized; everything else stays internal-only. The
+`@picloud/client` TypeScript package wraps typed HTTP, SSE, auth, and
+React/Svelte hooks. Plus three v1.1.5 follow-ups.
+
+### Added — Realtime
+
+- **`topics` registry** (`migrations/0021_topics.sql`) — pub/sub topics
+  are internal-only by default; a `topics` row with
+  `external_subscribable = true` opts one into external SSE subscription.
+  `auth_mode` is `'public'` or `'token'`.
+- **Topic admin endpoints** under `/api/v1/admin/apps/{id}/topics` —
+  `POST` (register), `GET` (list), `PATCH /{name}` (flip
+  external/auth_mode — its own audited surface), `DELETE /{name}`
+  (unregister + disconnect live subscribers). Gated by the new
+  `Capability::AppTopicManage` → `app:admin` scope (no new scope; the
+  seven-scope commitment holds).
+- **SSE endpoint `GET /realtime/topics/{topic}`** — data-plane surface
+  (deliberately not under `/api/`). Resolves `Host` → app, authorizes
+  via the `RealtimeAuthority` (404 for missing/internal topics, 401 for
+  bad/absent tokens), then streams `data: {topic,message,published_at}`
+  events with a configurable heartbeat (`PICLOUD_REALTIME_HEARTBEAT_SEC`,
+  default 30). Token via `Authorization: Bearer` or `?token=`.
+- **`RealtimeBroadcaster` + `RealtimeEvent` + `RealtimeAuthority`**
+  traits (`picloud-shared`); in-process `InProcessBroadcaster`
+  (`tokio::sync::broadcast`, per-channel capacity
+  `PICLOUD_REALTIME_BROADCAST_CAPACITY` default 64, periodic empty-channel
+  GC) and the DB-backed `RealtimeAuthorityImpl` (orchestrator-core /
+  manager-core respectively). The publish path now also fans out to
+  in-process SSE subscribers, best-effort, after the durable outbox
+  fan-out commits — a broadcast failure never fails the publish.
+- **`pubsub::subscriber_token(topics, ttl)`** Rhai SDK (SDK schema
+  1.6 → 1.7) — mints an HMAC-SHA256 subscriber token (URL-safe
+  `payload.signature`) scoped to externally-subscribable topics.
+  Requires an authenticated principal + the pub/sub publish capability.
+  TTL clamped to `[10s, 24h]` (default 1h), env-overridable via
+  `PICLOUD_SUBSCRIBER_TOKEN_TTL_{MIN,MAX,DEFAULT}_SEC`. Per-app signing
+  keys persist in the new `app_secrets` table
+  (`migrations/0022_app_secrets.sql`), created lazily on first mint. No
+  per-token revocation (rotation invalidates wholesale; short TTL is the
+  safety mechanism).
+- **Dashboard Topics tab** — register/list/edit/delete topics with a
+  prominent external/internal badge, auth-mode radio (conditional on
+  external), and a confirmation when flipping a topic external.
+
+### Added — `@picloud/client` (TypeScript, v1.0.0)
+
+- New top-level package `clients/typescript/` (tsup dual ESM+CJS +
+  `.d.ts`, vitest). Typed HTTP via `endpoint<Req,Res>(path).get()/.post()`
+  with auth-token injection and structured errors; SSE `subscribe(topic,
+  cb, {token, onTokenExpired})` with exponential-backoff reconnect,
+  401 token-refresh, and `Last-Event-ID` resume; `auth.login/logout/token`
+  over dev-defined endpoints; React (`useTopic`/`useEndpoint` +
+  `PicloudProvider`) and Svelte (`topicStore`/`endpointStore`) subpath
+  exports. Optional zod/valibot runtime validation via a `{ parse }`
+  adapter (no hard dep). Hybrid model: no direct service access from the
+  browser.
+
+### Changed / Fixed — v1.1.5 follow-ups
+
+- **Empty blobs accepted** — `NewFile::validate` / `FileUpdate::validate`
+  no longer reject zero-length `data`; empty files are a valid stored
+  state (sentinels, placeholders). Non-breaking.
+- **Orphan `*.tmp.*` sweeper** — a startup tokio task
+  (`spawn_files_orphan_sweep`) walks the files root every
+  `PICLOUD_FILES_ORPHAN_SWEEP_INTERVAL_SEC` (default 6h) and unlinks temp
+  blobs older than `PICLOUD_FILES_ORPHAN_TMP_TTL_SEC` (default 1h). No DB
+  cross-check (that full reconciler is v1.3+).
+- **Dispatcher end-to-end tests** — `crates/picloud/tests/dispatcher_e2e.rs`,
+  one per trigger kind (kv/docs/cron/files/pubsub/dead_letter),
+  DATABASE_URL-gated (skip cleanly when unset).
+
+### Notes
+
+- New deps: `hmac` (token signing, picloud-shared), `tokio-stream` (SSE
+  body stream, orchestrator-core).
+- New env vars: `PICLOUD_REALTIME_HEARTBEAT_SEC`,
+  `PICLOUD_REALTIME_BROADCAST_CAPACITY`,
+  `PICLOUD_SUBSCRIBER_TOKEN_TTL_{MIN,MAX,DEFAULT}_SEC`,
+  `PICLOUD_FILES_ORPHAN_SWEEP_INTERVAL_SEC`,
+  `PICLOUD_FILES_ORPHAN_TMP_TTL_SEC`.
+
 ## v1.1.5 — Files & Pub/Sub (unreleased)
 
 Two stateful services + two trigger kinds. **`files::*`** is