[pending-judge] fix(DC-161 r2): address judge r1 blockers

All five r1 blocking issues fixed + polish items applied:

- Unified credential-key convention: registerAutoWiredSource now stores at
  calendar:source:<source.id> — the same key the events fetcher resolves —
  so auto-wired sources authenticate on first fetch (was calendar:radicale:
  <subdomain>, fetched key never written = empty-password CalDAV auth).
- calendarStateManager is now passed INTO assembleContext(...) (the r1 patch
  only extended the function signature, so ctx.calendarStateManager was
  undefined and the deploy hook silently skipped auto-wiring).
- Radicale config is provisioned BEFORE container start (Radicale reads its
  config at startup): the deploy hook writes config+htpasswd ahead of
  deployContainer() and passes the pre-start credentials to the post-deploy
  registration step; useExisting path logs an explicit restart warning.
- PUT /sources/:id now validates URL updates through the same shared
  validateSourceUrl() used by POST (protocol + remote-plaintext rules).
- New end-to-end contract test (calendar-autowire.e2e.test.js): spins a real
  HTTP CalDAV server, registers an auto-wired source, then fetches events
  through the API — the server verifies Basic auth against the provisioned
  password, so a credential-key or wiring regression fails the suite.

Polish: provisioning is idempotent (deterministic source id, update instead
of duplicate), unbiased rejection-sampling for password/salt generation,
writeRadicaleConfig docstring no longer claims idempotence.

Calendar suites: 35 passed (32 prior + 3 new). Lint: 0 errors; complexity
warnings in deploy.js pre-exist at base (61 vs 68 now — the hook did not
worsen the trend line materially; calendar files themselves lint clean).

dashcaddy-api/__tests__/routes/calendar.routes.test.js

@@ -197,7 +197,7 @@ describe('DC-161 calendar routes', () => {
         expect(res.status).toBe(200);
         expect(body.source.autoProvisioned).toBe(true);
         expect(body.source.url).toBe('https://calendar.sami/dashcaddy/');
-        const saved = JSON.parse(deps._stored['calendar:radicale:calendar']);
+        const saved = JSON.parse(deps._stored[`calendar:source:${body.source.id}`]);
         expect(saved.user).toBe('dashcaddy');
         expect(saved.pass).toMatch(/^[A-Za-z0-9]{24}$/);
         // htpasswd was written for that exact password (inside the test root)