feat: add local SQLite cache with background sync and HA deployment

- Add SyncEngine for background sync between local SQLite cache and
  remote API with pending_ops queue for offline resilience
- Refactor MCP server to support three modes: SQLite-only, hybrid
  (local cache + sync, new default), and HTTP-only (legacy)
- Add GET /api/memories/sync endpoint for incremental sync
- Change DELETE to soft delete (set deleted_at) for sync support
- Add deleted_at IS NULL filters to all read queries
- Scale API deployment to 2 replicas with pod anti-affinity, PDB,
  and startup probe for high availability
- Add migration 003 for deleted_at column and updated_at index
- Add comprehensive tests for sync engine and API sync endpoint

src/claude_memory/api/models.py

@@ -1,4 +1,4 @@
-from typing import Optional
+from typing import Any, Optional
 
 from pydantic import BaseModel, Field
 
@@ -30,3 +30,8 @@ class SecretResponse(BaseModel):
     id: int
     content: str
     source: str  # "vault", "encrypted", "plaintext"
+
+
+class SyncResponse(BaseModel):
+    memories: list[dict[str, Any]]
+    server_time: str