Release v0.2.0: multiple named API keys per user

Replaces the single per-user DRF token with named, individually-revocable
API keys, so you can run one key per agent and cut off a leaked one without
disrupting the others.

- New ApiKey model (user, name, dbk_-prefixed key, created_at, last_used_at).
  Data migration copies every existing authtoken 1:1 into a "default" named
  key with the same value, so no client (incl. the sibling test project's
  hardcoded test-user key) needs reconfiguring.
- Auth (resolve_token_user) resolves against ApiKey and stamps last_used_at,
  throttled to one write/minute.
- Settings -> API Keys: table with name/key/created/last-used + per-row
  revoke and a create form; keys viewable on demand. Settings -> Account now
  links here; Settings -> Users issues a named initial key.
- Gated provisioning API for test installations: GET/POST /api/keys and
  DELETE /api/keys/{id}, controlled by DAYBOOK_KEY_PROVISIONING_API (unset ->
  follows DEBUG, so off in deployment). Advertised via key_provisioning_api
  in /api/capabilities; 403 when disabled.
- Docs (api/deployment/quickstart/posting-helper), SKILL.md, and env.example
  updated from "token / Settings -> Account" to "key / Settings -> API Keys".
- Tests: new API + UI suites for keys; existing token-based tests moved to
  ApiKey. Full suite 129 passing.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

static/daybook.css

@@ -990,6 +990,64 @@ kbd {
   word-break: break-all;
 }
 
+.muted {
+  color: var(--muted);
+}
+
+.api-key-create {
+  align-items: end;
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.75rem;
+  margin-bottom: 1.5rem;
+}
+
+.api-key-create label {
+  display: flex;
+  flex-direction: column;
+  font-weight: 600;
+  gap: 0.3rem;
+}
+
+.api-key-table {
+  border-collapse: collapse;
+  width: 100%;
+}
+
+.api-key-table th,
+.api-key-table td {
+  border-bottom: 1px solid var(--accent-border);
+  padding: 0.55rem 0.7rem;
+  text-align: left;
+  vertical-align: middle;
+}
+
+.api-key-table th {
+  color: var(--muted);
+  font-size: 0.85em;
+  font-weight: 600;
+}
+
+.api-key-cell {
+  align-items: center;
+  display: flex;
+  gap: 0.5rem;
+}
+
+.api-key-cell .token-value {
+  font-size: 0.85em;
+}
+
+.api-key-copy {
+  flex-shrink: 0;
+}
+
+.api-key-revoke {
+  background: var(--danger-bg);
+  border: 1px solid var(--danger-text);
+  color: var(--danger-text);
+}
+
 .about-head {
   align-items: center;
   display: flex;