feat: Sidecar V2 — multi-pool provider proxy with 429 cooldown

- proxy.py: Fix route path duplication (v1/v1 → v1) when upstream
  base URL already includes /v1 prefix
- proxy.py: Fix _emergency_count global variable for metrics tracking
- server.py: Add logging.basicConfig(level=logging.INFO) for structlog
  INFO-level log visibility
- Full multi-pool routing: primary → fallback → emergency passthrough
- Per-backend rate limiting with RPM-based token bucket
- 429 cooldown mechanism with automatic recovery
- Dashboard with SSE real-time monitoring
- Admin API for backend/pool/config management
- SQLite-backed persistence with encrypted API key storage
- Docker compose deployment

Deployed by opengineer 严维序 as BIZ-50 Step 4

storage/models.py

@@ -0,0 +1,161 @@
+"""Data models for Sidecar V2 — backend-centric, Canonical Name routing."""
+
+from dataclasses import dataclass, field, asdict
+from typing import Optional
+import json
+
+
+@dataclass
+class ModelMapping:
+    """A single model mapping within a backend: Canonical Name → native_id + properties."""
+
+    native_id: str
+    reasoning: bool = False
+    reasoning_effort: bool = False
+    input_modalities: list[str] = field(default_factory=lambda: ["text"])
+    cost: dict = field(default_factory=lambda: {
+        "input": 0.0, "output": 0.0, "cacheRead": 0.0, "cacheWrite": 0.0
+    })
+    context_window: int = 128000
+    max_tokens: int = 65536
+    compat: dict = field(default_factory=dict)
+
+    def to_dict(self) -> dict:
+        return asdict(self)
+
+    @classmethod
+    def from_dict(cls, d: dict) -> "ModelMapping":
+        defaults = {
+            "native_id": "",
+            "reasoning": False,
+            "reasoning_effort": False,
+            "input_modalities": ["text"],
+            "cost": {"input": 0.0, "output": 0.0, "cacheRead": 0.0, "cacheWrite": 0.0},
+            "context_window": 128000,
+            "max_tokens": 65536,
+            "compat": {},
+        }
+        defaults.update(d)
+        return cls(**{k: v for k, v in defaults.items() if k in cls.__dataclass_fields__})
+
+
+@dataclass
+class Backend:
+    """A physical API backend (API Key + URL).
+
+    Represents a single API key endpoint. Multiple backends can serve the same
+    Canonical Models through their model_mappings.
+    """
+
+    id: str = ""
+    name: str = ""
+    label: str = ""  # e.g., "nvidia", "siliconflow" — WebUI tag only
+    api_base_url: str = ""
+    api_key_encrypted: str = ""
+    api: str = "openai-completions"
+    timeout_seconds: int = 120
+    rpm_limit: int = 40
+    pool: str = "primary"  # primary | fallback
+    enabled: bool = True
+    status: str = "healthy"  # healthy | cooling | error | disabled
+    model_mappings: dict[str, ModelMapping] = field(default_factory=dict)
+    source: str = "webui"  # webui | env | import
+    cooldown_until: Optional[str] = None
+    consecutive_429_count: int = 0
+    metadata: dict = field(default_factory=dict)
+    created_at: str = ""
+    updated_at: str = ""
+
+    # Runtime fields (not persisted)
+    api_key_plain: str = ""  # decrypted at load time, not serialized to DB
+
+    def has_model(self, canonical_name: str) -> bool:
+        """Check if backend supports a given Canonical Model."""
+        return canonical_name in self.model_mappings
+
+    def get_native_id(self, canonical_name: str) -> str:
+        """Get this backend's native model ID for a Canonical Name."""
+        mm = self.model_mappings.get(canonical_name)
+        return mm.native_id if mm else canonical_name
+
+    def get_model_cost(self, canonical_name: str) -> dict:
+        """Get cost info for a Canonical Model on this backend."""
+        mm = self.model_mappings.get(canonical_name)
+        return mm.cost if mm else {"input": 0.0, "output": 0.0, "cacheRead": 0.0, "cacheWrite": 0.0}
+
+    def to_dict(self, mask_key: bool = True) -> dict:
+        """Convert to dict for API responses."""
+        d = asdict(self)
+        # Remove runtime-only fields
+        d.pop("api_key_plain", None)
+        d.pop("api_key_encrypted", None)
+
+        # Mask API key
+        if mask_key and self.api_key_plain:
+            d["api_key"] = _mask_key(self.api_key_plain)
+        elif self.api_key_plain:
+            d["api_key"] = self.api_key_plain
+        else:
+            d["api_key"] = ""
+
+        # Convert model_mappings to dict for serialization
+        d["model_mappings"] = {
+            k: v.to_dict() for k, v in self.model_mappings.items()
+        }
+        return d
+
+
+def _mask_key(key: str) -> str:
+    if len(key) <= 10:
+        return key[:2] + "****"
+    return key[:6] + "****" + key[-4:]
+
+
+@dataclass
+class CooldownEvent:
+    id: str = ""
+    backend_id: str = ""
+    consecutive_count: int = 1
+    cooldown_seconds: int = 60
+    response_summary: str = ""
+    started_at: str = ""
+    ended_at: Optional[str] = None
+
+
+@dataclass
+class BackendHealth:
+    backend_id: str = ""
+    state: str = "healthy"  # healthy | degraded | down
+    last_latency_ms: int = 0
+    last_status_code: int = 200
+    success_rate_5m: float = 1.0
+    consecutive_failures: int = 0
+    last_check_at: str = ""
+
+
+@dataclass
+class UsageLog:
+    id: str = ""
+    backend_id: str = ""
+    model: str = "unknown"
+    prompt_tokens: int = 0
+    completion_tokens: int = 0
+    total_tokens: int = 0
+    cost: float = 0.0
+    request_count: int = 0
+    error_count: int = 0
+    avg_latency_ms: int = 0
+    ttft_ms: int = 0
+    hour_bucket: str = ""
+
+
+@dataclass
+class DailyStats:
+    id: str = ""
+    date: str = ""
+    pool: str = "primary"
+    total_requests: int = 0
+    total_errors: int = 0
+    total_tokens: int = 0
+    total_cost: float = 0.0
+    unique_backends: int = 0