Refactor: Consolidate service/offer architecture

## Breaking Changes

### Server
- Services can now have multiple offers instead of single offer
- POST /users/:username/services accepts `offers` array instead of `sdp`
- GET /users/:username/services/:fqn returns `offers` array in response
- GET /services/:uuid returns `offers` array in response
- Database schema: removed `offer_id` from services table, added `service_id` to offers table
- Added `batchCreateServices()` and `getOffersForService()` methods

### Client
- `PublishServiceOptions` interface: `offers` array instead of `sdp` string
- `Service` interface: `offers` array instead of `offerId` and `sdp`
- `ServiceRequest` interface: `offers` array instead of `sdp`
- RondevuSignaler.setOffer() sends offers array to server
- Updated to extract offerId from first offer in service response

## New Features
- Support for multiple simultaneous offers per service (connection pooling)
- Batch service creation endpoint for reduced server load
- Proper one-to-many relationship between services and offers

## Implementation Details

### Server Changes (src/storage/)
- sqlite.ts: Added service_id column to offers, removed offer_id from services
- d1.ts: Updated to match new interface
- types.ts: Updated interfaces for Service, Offer, CreateServiceRequest
- app.ts: Updated all service endpoints to handle offers array

### Client Changes (src/)
- api.ts: Added OfferRequest and ServiceOffer interfaces
- rondevu-service.ts: Updated PublishServiceOptions to use offers array
- rondevu-signaler.ts: Updated to send/receive offers array

## Migration Notes
- No backwards compatibility - this is a breaking change
- Services published with old API will not work with new server
- Clients must update to new API to work with updated server

🤖 Generated with Claude Code

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "@xtr-dev/rondevu-server",
-  "version": "0.1.5",
+  "version": "0.2.5",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@xtr-dev/rondevu-server",
-      "version": "0.1.5",
+      "version": "0.2.5",
       "dependencies": {
         "@hono/node-server": "^1.19.6",
         "@noble/ed25519": "^3.0.0",