feat(ralph): rate limit budget tracking + whatsapp text-keywords

Task #1 — Rate limit budget tracking MVP:
- tools/ralph_usage.py: pure functions (extract_usage_entry, parse_usage_jsonl,
  aggregate_by_day/_project, filter_by_days, summarize) + CLI append/summarize
  subcommands. Atomic write via temp+rename.
- tools/ralph/ralph.sh: după fiecare claude -p, append usage entry
  derivat din JSON envelope la <project>/scripts/ralph/usage.jsonl. Best-effort,
  niciodată blochează rularea (|| true).
- dashboard/handlers/ralph.py: GET /api/ralph/usage[?days=N] aggregează cross-
  project și returnează {today_cost, today_runs, by_project, by_day, ...}.

Task #2 — WhatsApp text-keyword commands:
- src/router.py: helper _translate_whatsapp_text mapează "aprob"/"stop <slug>"/
  "stare [<slug>]" → /a, /k, /l. Apelat DOAR pe adapter whatsapp în
  _try_ralph_dispatch (Discord/TG nu sunt afectate). NU acoperim propose
  intentionat — descrierea liberă e prea fragilă pentru parsing text-only.

Tests: 49 noi (test_ralph_usage 28 + test_whatsapp_keywords 21) + 4 noi în
test_dashboard_ralph_endpoint pentru /api/ralph/usage. Toate trec; regression
suite (test_router, test_router_planning, test_dashboard_ralph_endpoint,
test_whatsapp) — 90/90 pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

dashboard/api.py

@@ -159,6 +159,8 @@ 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('/')