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/models/technical_debt.py

@@ -1,19 +1,51 @@
 import enum
 import uuid
 
-from sqlalchemy import Enum, ForeignKey, String, Text
+from sqlalchemy import DateTime, Enum, ForeignKey, String, Text
 from sqlalchemy.dialects.postgresql import UUID
 from sqlalchemy.orm import Mapped, mapped_column, relationship
+from sqlalchemy.sql import func
 
 from api.models.base import Base, TimestampMixin, new_uuid
 
 
 class TDStatus(str, enum.Enum):
+    # Legacy general statuses
     open = "open"
     in_progress = "in_progress"
     resolved = "resolved"
     deferred = "deferred"
     wont_fix = "wont_fix"
+    # Dashboard-improvement workflow steps
+    submitted = "submitted"
+    analyse = "analyse"
+    plan = "plan"
+    implement = "implement"
+    test = "test"
+    review = "review"
+    finished = "finished"
+
+
+# Ordered workflow steps for dashboard-improvement suggestions
+SUGGESTION_STEPS = ["submitted", "analyse", "plan", "implement", "test", "review", "finished"]
+
+
+class TDNote(Base):
+    __tablename__ = "td_notes"
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=new_uuid)
+    td_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("technical_debt.id", ondelete="CASCADE"),
+        nullable=False, index=True,
+    )
+    step: Mapped[str] = mapped_column(String(30), nullable=False)
+    author: Mapped[str | None] = mapped_column(String(100), nullable=True)
+    content: Mapped[str] = mapped_column(Text, nullable=False)
+    created_at: Mapped[DateTime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), nullable=False
+    )
+
+    td: Mapped["TechnicalDebt"] = relationship("TechnicalDebt", back_populates="notes")
 
 
 class TechnicalDebt(Base, TimestampMixin):
@@ -51,6 +83,10 @@ class TechnicalDebt(Base, TimestampMixin):
     domain: Mapped["Domain"] = relationship("Domain", lazy="selectin")  # noqa: F821
     topic: Mapped["Topic"] = relationship("Topic", lazy="selectin")  # noqa: F821
     workstream: Mapped["Workstream"] = relationship("Workstream", lazy="selectin")  # noqa: F821
+    notes: Mapped[list["TDNote"]] = relationship(
+        "TDNote", back_populates="td", lazy="selectin",
+        order_by="TDNote.created_at",
+    )
 
     @property
     def domain_slug(self) -> str: