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

src/storage/d1.ts

@@ -401,6 +401,7 @@ export class D1Storage implements Storage {
   async createService(request: CreateServiceRequest): Promise<{
     service: Service;
     indexUuid: string;
+    offers: Offer[];
   }> {
     const serviceId = crypto.randomUUID();
     const indexUuid = crypto.randomUUID();
@@ -408,13 +409,12 @@ export class D1Storage implements Storage {
 
     // Insert service
     await this.db.prepare(`
-      INSERT INTO services (id, username, service_fqn, offer_id, created_at, expires_at, is_public, metadata)
-      VALUES (?, ?, ?, ?, ?, ?, ?, ?)
+      INSERT INTO services (id, username, service_fqn, created_at, expires_at, is_public, metadata)
+      VALUES (?, ?, ?, ?, ?, ?, ?)
     `).bind(
       serviceId,
       request.username,
       request.serviceFqn,
-      request.offerId,
       now,
       request.expiresAt,
       request.isPublic ? 1 : 0,
@@ -434,6 +434,13 @@ export class D1Storage implements Storage {
       request.expiresAt
     ).run();
 
+    // Create offers with serviceId
+    const offerRequests = request.offers.map(offer => ({
+      ...offer,
+      serviceId,
+    }));
+    const offers = await this.createOffers(offerRequests);
+
     // Touch username to extend expiry
     await this.touchUsername(request.username);
 
@@ -442,16 +449,43 @@ export class D1Storage implements Storage {
         id: serviceId,
         username: request.username,
         serviceFqn: request.serviceFqn,
-        offerId: request.offerId,
         createdAt: now,
         expiresAt: request.expiresAt,
         isPublic: request.isPublic || false,
         metadata: request.metadata,
       },
       indexUuid,
+      offers,
     };
   }
 
+  async batchCreateServices(requests: CreateServiceRequest[]): Promise<Array<{
+    service: Service;
+    indexUuid: string;
+    offers: Offer[];
+  }>> {
+    const results = [];
+    for (const request of requests) {
+      const result = await this.createService(request);
+      results.push(result);
+    }
+    return results;
+  }
+
+  async getOffersForService(serviceId: string): Promise<Offer[]> {
+    const result = await this.db.prepare(`
+      SELECT * FROM offers
+      WHERE service_id = ? AND expires_at > ?
+      ORDER BY created_at ASC
+    `).bind(serviceId, Date.now()).all();
+
+    if (!result.results) {
+      return [];
+    }
+
+    return result.results.map(row => this.rowToOffer(row as any));
+  }
+
   async getServiceById(serviceId: string): Promise<Service | null> {
     const result = await this.db.prepare(`
       SELECT * FROM services
@@ -560,7 +594,6 @@ export class D1Storage implements Storage {
       id: row.id,
       username: row.username,
       serviceFqn: row.service_fqn,
-      offerId: row.offer_id,
       createdAt: row.created_at,
       expiresAt: row.expires_at,
       isPublic: row.is_public === 1,