fix(status-enum): add paused to ProjectStatus, validate, fix progress

Drift-audit Group 6 + Group 5 #6 (enum-extension / status drift):

- ProjectStatus gains 'paused' — routes and frontend already treated it as
  first-class, but the enum (the source of truth) omitted it and the error
  strings lied. A future CHECK derived from the enum would have rejected
  existing paused rows.
- create_project/update_project now validate status via ProjectStatus at the
  service layer (canonical gate; notes.status has no DB CHECK), so the MCP
  create/update_project path can't persist a typo'd status. MCP docstrings
  realigned to the 4-value domain; route error strings corrected.
- get_milestone_progress: cancelled tasks are excluded from the percent
  denominator (and now reported in status_counts), so a milestone whose only
  open task was cancelled reaches 100% instead of stalling below it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/fabledassistant/services/projects.py

@@ -6,11 +6,25 @@ from sqlalchemy import func, select
 
 from fabledassistant.models import async_session
 from fabledassistant.models.note import Note
-from fabledassistant.models.project import Project
+from fabledassistant.models.project import Project, ProjectStatus
 
 logger = logging.getLogger(__name__)
 
 
+def _validate_status(status: str) -> str:
+    """Coerce/validate a project status against ProjectStatus.
+
+    Canonical gate so the MCP create/update_project path (which passes status
+    straight through) can't persist an out-of-enum value — there's no DB CHECK.
+    """
+    try:
+        return ProjectStatus(status).value
+    except ValueError:
+        raise ValueError(
+            f"Invalid status: {status!r}. Must be one of: {[s.value for s in ProjectStatus]}"
+        )
+
+
 async def create_project(
     user_id: int,
     title: str,
@@ -19,6 +33,7 @@ async def create_project(
     color: str | None = None,
     status: str = "active",
 ) -> Project:
+    status = _validate_status(status)
     async with async_session() as session:
         project = Project(
             user_id=user_id,
@@ -87,6 +102,8 @@ async def update_project(user_id: int, project_id: int, **fields: object) -> Pro
         project = result.scalars().first()
         if project is None:
             return None
+        if "status" in fields and fields["status"] is not None:
+            fields["status"] = _validate_status(fields["status"])
         for key, value in fields.items():
             if hasattr(project, key):
                 setattr(project, key, value)