refactor(coordinator-api): make rate limits configurable via environment variables

- Add configurable rate limit settings for all endpoints (jobs, miner, admin, marketplace, exchange)
- Replace hardcoded rate limit decorators with lambda functions reading from settings
- Add rate limit configuration logging during startup
- Implement custom RateLimitExceeded exception handler with structured error responses
- Add enhanced shutdown logging for database cleanup and resource management
- Set default rate

apps/coordinator-api/src/app/routers/client.py

@@ -7,6 +7,7 @@ from ..schemas import JobCreate, JobView, JobResult, JobPaymentCreate
 from ..types import JobState
 from ..services import JobService
 from ..services.payments import PaymentService
+from ..config import settings
 from ..storage import SessionDep
 
 limiter = Limiter(key_func=get_remote_address)
@@ -14,7 +15,7 @@ router = APIRouter(tags=["client"])
 
 
 @router.post("/jobs", response_model=JobView, status_code=status.HTTP_201_CREATED, summary="Submit a job")
-@limiter.limit("100/minute")
+@limiter.limit(lambda: settings.rate_limit_jobs_submit)
 async def submit_job(
     req: JobCreate,
     request: Request,

apps/coordinator-api/src/app/routers/miner.py

@@ -9,6 +9,7 @@ from ..deps import require_miner_key
 from ..schemas import AssignedJob, JobFailSubmit, JobResultSubmit, JobState, MinerHeartbeat, MinerRegister, PollRequest
 from ..services import JobService, MinerService
 from ..services.receipts import ReceiptService
+from ..config import settings
 from ..storage import SessionDep
 from aitbc.logging import get_logger
 
@@ -18,7 +19,7 @@ router = APIRouter(tags=["miner"])
 
 
 @router.post("/miners/register", summary="Register or update miner")
-@limiter.limit("30/minute")
+@limiter.limit(lambda: settings.rate_limit_miner_register)
 async def register(
     req: MinerRegister,
     request: Request,
@@ -30,7 +31,7 @@ async def register(
     return {"status": "ok", "session_token": record.session_token}
 
 @router.post("/miners/heartbeat", summary="Send miner heartbeat")
-@limiter.limit("60/minute")
+@limiter.limit(lambda: settings.rate_limit_miner_heartbeat)
 async def heartbeat(
     req: MinerHeartbeat,
     request: Request,