M9: MCP Hub locale/correlation propagation, real Hub health check, fix stale test image

Fixed two concrete gaps in the MCP knowledge-search endpoint: no locale field
existed at all (now nl-BE/en-GB/fr-BE, wired to the knowledge provider's
existing language param), and the correlation ID was always freshly minted,
ignoring any inbound X-Correlation-Id header. Added a shared dependency and
applied it to all four MCP endpoints so Fleet Ops's own audit log preserves
the Hub's real correlation ID end to end.

MCP_HUB_BASE_URL/MCP_PROVIDER_ID were declared in .env.example but never read
anywhere. Since the Hub's own registration is catalog-driven (it never needs
Fleet Ops to push a registration call), wired mcp_hub_base_url for a real Hub
reachability health check instead of an unneeded self-registration call.

Renamed Fleet Ops's own internal audit tool labels mobilityops_* -> fleet_ops_*
(mirrored in contracts/mcp-tools.json with mobilityops_* kept as deprecated
aliases); documented that the live Hub connector's own dotted tool namespace
is a separate, Hub-owned naming layer, deliberately not touched.

Automation page's MCP card now shows real evidence (last tool/client/count/
timestamp, honest no-evidence state) instead of just the registration flag.

Also fixed a real methodology gap found mid-session: compose.yaml's api
service has no bind mount, so `docker compose run --rm api` silently tests a
stale image until rebuilt. Re-ran every local gate after rebuilding; fixed one
genuinely stale test assertion and two lint line-length errors surfaced by
that rebuild. 176 tests passing, ruff clean, mypy clean (50 files).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/app/schemas.py

@@ -284,6 +284,7 @@ class McpHubIntegrationStatus(BaseModel):
     last_tool: str | None = None
     last_client: str | None = None
     last_called_at: datetime | None = None
+    hub_reachable: bool | None = None
 
 
 class IntegrationStatusOut(BaseModel):
@@ -403,6 +404,7 @@ class McpVehicleDetailOut(BaseModel):
 class McpKnowledgeSearchRequest(BaseModel):
     question: str = Field(min_length=3, max_length=1000)
     max_sources: int = Field(default=4, ge=1, le=8)
+    locale: Literal["nl-BE", "en-GB", "fr-BE"] = "en-GB"
 
 
 class AuditEventOut(BaseModel):