feat(17-02): SNMP profile CRUD API and SNMP metrics query endpoint

- Add Pydantic schemas for SNMP profile CRUD (list excludes profile_data JSONB)
- Add 5-route SNMP profiles router with system profile protection (403)
- Add device deletion protection for referenced profiles (409)
- Add time-bucketed SNMP metrics query endpoint with metric_name/group filters
- Add distinct metric names endpoint for frontend dropdowns
- Register snmp_profiles_router in main.py

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/schemas/snmp_profile.py

@@ -0,0 +1,93 @@
+"""Pydantic schemas for SNMP Profile CRUD endpoints."""
+
+import uuid
+from datetime import datetime
+from typing import Optional
+
+from pydantic import BaseModel, field_validator
+
+
+VALID_CATEGORIES = {"switch", "router", "access_point", "ups", "printer", "server", "generic"}
+
+
+class SNMPProfileCreate(BaseModel):
+    """Schema for creating a tenant-scoped SNMP profile."""
+
+    name: str
+    description: Optional[str] = None
+    sys_object_id: Optional[str] = None
+    vendor: Optional[str] = None
+    category: Optional[str] = None
+    profile_data: dict
+
+    @field_validator("name")
+    @classmethod
+    def validate_name(cls, v: str) -> str:
+        v = v.strip()
+        if len(v) < 1 or len(v) > 255:
+            raise ValueError("Profile name must be 1-255 characters")
+        return v
+
+    @field_validator("category")
+    @classmethod
+    def validate_category(cls, v: Optional[str]) -> Optional[str]:
+        if v is not None and v not in VALID_CATEGORIES:
+            raise ValueError(f"Category must be one of: {', '.join(sorted(VALID_CATEGORIES))}")
+        return v
+
+
+class SNMPProfileUpdate(BaseModel):
+    """Schema for updating an SNMP profile. All fields optional."""
+
+    name: Optional[str] = None
+    description: Optional[str] = None
+    sys_object_id: Optional[str] = None
+    vendor: Optional[str] = None
+    category: Optional[str] = None
+    profile_data: Optional[dict] = None
+
+    @field_validator("name")
+    @classmethod
+    def validate_name(cls, v: Optional[str]) -> Optional[str]:
+        if v is None:
+            return v
+        v = v.strip()
+        if len(v) < 1 or len(v) > 255:
+            raise ValueError("Profile name must be 1-255 characters")
+        return v
+
+    @field_validator("category")
+    @classmethod
+    def validate_category(cls, v: Optional[str]) -> Optional[str]:
+        if v is not None and v not in VALID_CATEGORIES:
+            raise ValueError(f"Category must be one of: {', '.join(sorted(VALID_CATEGORIES))}")
+        return v
+
+
+class SNMPProfileResponse(BaseModel):
+    """SNMP profile response (list view -- excludes large profile_data JSONB)."""
+
+    id: uuid.UUID
+    tenant_id: Optional[uuid.UUID] = None
+    name: str
+    description: Optional[str] = None
+    sys_object_id: Optional[str] = None
+    vendor: Optional[str] = None
+    category: Optional[str] = None
+    is_system: bool
+    created_at: datetime
+    updated_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class SNMPProfileDetailResponse(SNMPProfileResponse):
+    """SNMP profile detail response (includes full profile_data)."""
+
+    profile_data: dict
+
+
+class SNMPProfileListResponse(BaseModel):
+    """List of SNMP profiles."""
+
+    profiles: list[SNMPProfileResponse]