Merge branch 'ralph/instrumentation' — rate limit budget + WhatsApp keywords

Rate limit budget tracking (TODO P2):
- tools/ralph_usage.py — pure functions extract/parse/aggregate; CLI subcomenzi
  append/summarize. Atomic write JSONL.
- tools/ralph/ralph.sh: după fiecare claude -p, append usage entry la
  workspace/<slug>/scripts/ralph/usage.jsonl (best-effort)
- dashboard/handlers/ralph.py: GET /api/ralph/usage[?days=N] cross-project
  aggregation cu today_cost, today_runs, by_project, by_day

WhatsApp text-keyword commands (TODO P3):
- src/router.py: helper _translate_whatsapp_text — `aprob <slug>` → `/a <slug>`,
  `stop <slug>` → `/k <slug>`, `stare`/`stare <slug>` → `/l`/`/l <slug>`. Aplicat
  DOAR pe adapter whatsapp în _try_ralph_dispatch (Discord/TG nu sunt afectate).
  Propose intentionally NOT covered (descrierea fragilă).

Tests: 53 noi (28 ralph_usage + 21 whatsapp_keywords + 4 dashboard endpoint extend)
+ 0 regressions pe modulele atinse.

dashboard/api.py

@@ -163,6 +163,8 @@ class TaskBoardHandler(
             self.handle_eco_doctor()
         elif self.path == '/api/ralph/status' or self.path.startswith('/api/ralph/status?'):
             self.handle_ralph_status()
+        elif self.path == '/api/ralph/usage' or self.path.startswith('/api/ralph/usage?'):
+            self.handle_ralph_usage()
         elif self.path.startswith('/api/ralph/'):
             # /api/ralph/<slug>/log or /api/ralph/<slug>/prd
             parts = self.path.split('?', 1)[0].split('/')