feat: complete Git Repo Manager MVP implementation

Backend (Phase 1-6):
- Pydantic schemas for request/response validation
- Service layer (SSH Key, Server, Repo, Sync)
- API routes with authentication
- FastAPI main application with lifespan management
- ORM models (SshKey, Server, Repo, SyncLog)

Frontend (Phase 7):
- Vue 3 + Element Plus + Pinia + Vue Router
- API client with Axios and interceptors
- State management stores
- All page components (Dashboard, Servers, Repos, SyncLogs, SshKeys, Settings)

Deployment (Phase 8):
- README with quick start guide
- Startup script (start.sh)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/schemas/common.py

@@ -0,0 +1,55 @@
+"""
+Common Pydantic schemas for API responses.
+"""
+from typing import Generic, TypeVar, Optional
+from pydantic import BaseModel, Field
+
+
+T = TypeVar("T")
+
+
+class SuccessResponse(BaseModel, Generic[T]):
+    """
+    Standard success response wrapper.
+    """
+    code: int = Field(default=0, description="Response code, 0 for success")
+    data: T = Field(description="Response data")
+    message: str = Field(default="success", description="Response message")
+
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "code": 0,
+                    "data": {},
+                    "message": "success"
+                }
+            ]
+        }
+    }
+
+
+class ErrorResponse(BaseModel):
+    """
+    Standard error response wrapper.
+    """
+    code: int = Field(description="Error code, non-zero for errors")
+    message: str = Field(description="Error message")
+    data: Optional[dict] = Field(default=None, description="Additional error data")
+
+    model_config = {
+        "json_schema_extra": {
+            "examples": [
+                {
+                    "code": 400,
+                    "message": "Bad request",
+                    "data": None
+                },
+                {
+                    "code": 404,
+                    "message": "Resource not found",
+                    "data": {"detail": "Item with id 123 not found"}
+                }
+            ]
+        }
+    }