feat(repos): multi-machine path support via host_paths

Adds a JSONB column `host_paths` to managed_repos mapping
hostname → absolute local path. Fixes the consistency-checker
failure when the same repo lives at different paths on different
machines (e.g. /home/worsch/marki-docx on the workstation vs
/home/tegwick/marki-docx on custodiancore).

Changes:
- Migration g4b5c6d7e8f9: adds host_paths JSONB (default {})
- Model: host_paths Mapped[dict] column
- Schemas: host_paths in RepoRead; new RepoPathRegister schema
- Router: POST /repos/{slug}/paths/ — merges one host entry
- consistency_check.py: resolve_repo_path() prefers host_paths
  [hostname] over local_path; --repo-path CLI override added
- MCP: update_repo_path(slug, path, host?) tool
- Makefile: register-path target; REPO_PATH passthrough on
  check-consistency and fix-consistency targets
- TOOLS.md: documents update_repo_path

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

api/schemas/managed_repo.py

@@ -24,6 +24,12 @@ class RepoUpdate(BaseModel):
     last_state_synced_at: datetime | None = None
 
 
+class RepoPathRegister(BaseModel):
+    """Register a machine-local path for a repo on a specific host."""
+    host: str
+    path: str
+
+
 class RepoRead(BaseModel):
     model_config = ConfigDict(from_attributes=True)
     id: uuid.UUID
@@ -32,6 +38,7 @@ class RepoRead(BaseModel):
     slug: str
     name: str
     local_path: str | None = None
+    host_paths: dict = {}
     remote_url: str | None = None
     description: str | None = None
     status: str