refactor: split services/docker.py into docker/ package

Split monolithic docker.py into focused modules:
- docker/compose.py — compose generation, execute_compose_command, volume sorting
- docker/container.py — container status, IP, logs, network, port finding
- docker/config_staging.py — instance dir, env file, config file staging
- docker/tunnel.py — cloudflared tunnel lifecycle (moved from services/tunnel.py)
- docker/__init__.py — re-exports all public symbols for backward compatibility
- services/tunnel.py — thin re-export wrapper for backward compatibility

Also includes schema extraction files created in prior work:
- schemas/config/config_profile.py
- schemas/project/*.py
- schemas/system/health.py
- schemas/tool/*.py
- schemas/user/*.py

All existing imports like 'from src.services.docker import X' and
'from src.services.tunnel import X' continue to work unchanged.

Quality gates: py_compile passed, ruff passed, import test passed.

apps/api/src/schemas/system/health.py

@@ -0,0 +1,50 @@
+"""Health check response schemas."""
+
+from pydantic import BaseModel, Field
+
+
+class DatabaseHealth(BaseModel):
+    """Database health check result."""
+
+    status: str = Field(description="Database health status", examples=["healthy"])
+    response_time_ms: float = Field(
+        description="Query response time in milliseconds", examples=[5.2]
+    )
+
+
+class DiskHealth(BaseModel):
+    """Disk space health check result."""
+
+    status: str = Field(description="Disk health status", examples=["healthy"])
+    free_gb: float = Field(description="Free disk space in GB", examples=[45.2])
+    total_gb: float = Field(description="Total disk space in GB", examples=[100.0])
+
+
+class HealthChecks(BaseModel):
+    """Individual health checks."""
+
+    database: DatabaseHealth | None = None
+    disk: DiskHealth | None = None
+
+
+class HealthResponse(BaseModel):
+    """Overall health check response."""
+
+    status: str = Field(description="Overall health status", examples=["healthy"])
+    timestamp: str = Field(
+        description="ISO 8601 timestamp", examples=["2026-05-19T12:00:00Z"]
+    )
+    version: str = Field(description="API version", examples=["0.1.0"])
+    checks: HealthChecks = Field(description="Individual health checks")
+    uptime_seconds: float = Field(
+        description="Server uptime in seconds", examples=[3600.0]
+    )
+
+
+class DatabaseHealthResponse(BaseModel):
+    """Database-specific health check response."""
+
+    status: str = Field(description="Database health status", examples=["healthy"])
+    response_time_ms: float = Field(
+        description="Query response time in milliseconds", examples=[5.2]
+    )