feat(suggestions): full suggestion workflow with per-step notes

DB migration h5c6d7e8f9a0:
- Extends tdstatus enum: submitted → analyse → plan → implement →
  test → review → finished (+ wont_fix remains)
- New td_notes table: td_id FK (CASCADE), step, author, content, created_at

API:
- TDNote model + TDNoteCreate/TDNoteRead schemas
- TDRead includes notes[] (selectin loaded)
- New routes: GET/POST /technical-debt/{id}/notes/
- list_td status filter accepts str (all enum values)

Modal: new submissions use status="submitted" instead of "open"

UI Feedback page revamp:
- Visual step-by-step stepper (submitted→analyse→plan→implement→test→review→finished)
- Per-step notes: view all notes, add note inline
- Action buttons: advance to next step, won't fix
- Review step highlighted as awaiting original suggester confirmation
- Closed items (finished/wont_fix) shown with last 2 notes

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

api/schemas/technical_debt.py

@@ -8,6 +8,23 @@ from api.models.technical_debt import TDStatus
 VALID_SEVERITIES = {"low", "medium", "high", "critical"}
 
 
+class TDNoteCreate(BaseModel):
+    step: str
+    author: str | None = None
+    content: str
+
+
+class TDNoteRead(BaseModel):
+    model_config = ConfigDict(from_attributes=True)
+
+    id: uuid.UUID
+    td_id: uuid.UUID
+    step: str
+    author: str | None = None
+    content: str
+    created_at: datetime
+
+
 class TDCreate(BaseModel):
     td_id: str | None = None
     domain: str  # slug; router resolves to domain_id FK
@@ -47,3 +64,4 @@ class TDRead(BaseModel):
     workstream_id: uuid.UUID | None = None
     created_at: datetime
     updated_at: datetime
+    notes: list[TDNoteRead] = []