feat: read the real gitea backlog into the app (P1 thin slice)

The app now displays its own live backlog instead of fixtures. First
end of the sync loop — the tap-root (#1) grows list reads and a read
path through the Electron main process.

- @commitea/core: client gains `listIssues` (paginated, PRs excluded)
  and `listMilestones`; a `lifecycle-v0` mapper (closed→done,
  labelled/milestoned→triage, bare→diagnosis — steeping/review await
  event inference in P1-5). +10 unit tests.
- main: gitea bridge over IPC (token stays in main, never the renderer);
  config from env / .env.local; gated off under COMMITEA_E2E so the
  committed e2e stays on fixtures. Preload exposes the typed bridge.
- renderer: useBacklog() reconciles once on mount; issuesToBoardColumns
  shapes real issues into The pot. Board takes optional real columns +
  a loading state, falling back to demo fixtures when unconfigured.

Verified: 14 e2e green (fixture mode) + a gated live spec that launches
against the real repo — the board renders the actual 25 open + 9 closed
issues (screenshot). SQLite mirror + reconcile-on-a-timer + lifecycle
event inference are the next slices (#2/#3/#5).

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

apps/desktop/src/preload/index.ts

@@ -1,7 +1,15 @@
-import { contextBridge } from 'electron'
+import { contextBridge, ipcRenderer } from 'electron'
 
 const api = {
   platform: process.platform,
+  gitea: {
+    /** Whether the main process has a gitea token + target repo configured. */
+    status: () => ipcRenderer.invoke('gitea:status'),
+    /** Full read of the managed repo — every issue + milestone. */
+    reconcile: () => ipcRenderer.invoke('gitea:reconcile'),
+    /** One issue by index, normalized (or null if unconfigured). */
+    getIssue: (index: number) => ipcRenderer.invoke('gitea:getIssue', index),
+  },
 }
 
 export type CommiteaApi = typeof api