Finish CUST-WP-0011 and implement STATE-WP-0061 suggestion backlog.

Add persisted Suggestion entities with WSJF ranking, relevance bumps,
REST/MCP write surfaces, /suggestions dashboard page, and daily triage
digest integration. Document the cluster operating model, archive the
completed migration workplan, and seed WARDEN-WP-0012 routing scenarios.

api/models/suggestion.py

@@ -0,0 +1,120 @@
+import enum
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, Enum, Float, ForeignKey, Integer, 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 SuggestionStage(str, enum.Enum):
+    suggestion = "suggestion"
+    requirement = "requirement"
+    promoted = "promoted"
+    declined = "declined"
+
+
+OPEN_SUGGESTION_STAGES = (SuggestionStage.suggestion, SuggestionStage.requirement)
+
+
+class Suggestion(Base, TimestampMixin):
+    __tablename__ = "suggestions"
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True), primary_key=True, default=new_uuid
+    )
+    domain_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("domains.id", ondelete="RESTRICT"),
+        nullable=False,
+        index=True,
+    )
+    topic_id: Mapped[uuid.UUID | None] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("topics.id", ondelete="SET NULL"), nullable=True
+    )
+    workplan_id: Mapped[uuid.UUID | None] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("workplans.id", ondelete="SET NULL"), nullable=True
+    )
+    title: Mapped[str] = mapped_column(String(500), nullable=False)
+    description: Mapped[str | None] = mapped_column(Text, nullable=True)
+    origin: Mapped[str | None] = mapped_column(String(200), nullable=True)
+    origin_ref: Mapped[str | None] = mapped_column(String(200), nullable=True, index=True)
+    stage: Mapped[SuggestionStage] = mapped_column(
+        Enum(SuggestionStage, name="suggestionstage"),
+        nullable=False,
+        default=SuggestionStage.suggestion,
+        index=True,
+    )
+    relevance: Mapped[int] = mapped_column(Integer, nullable=False, default=0, server_default="0")
+    relevance_events: Mapped[int] = mapped_column(
+        Integer, nullable=False, default=0, server_default="0"
+    )
+    last_requested_at: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
+    base_value: Mapped[float] = mapped_column(Float, nullable=False, default=3.0, server_default="3")
+    job_size: Mapped[float] = mapped_column(Float, nullable=False, default=3.0, server_default="3")
+    relevance_weight: Mapped[float] = mapped_column(
+        Float, nullable=False, default=1.0, server_default="1"
+    )
+    promoted_task_id: Mapped[uuid.UUID | None] = mapped_column(
+        UUID(as_uuid=True), ForeignKey("tasks.id", ondelete="SET NULL"), nullable=True
+    )
+
+    domain: Mapped["Domain"] = relationship("Domain", lazy="selectin")  # noqa: F821
+    topic: Mapped["Topic | None"] = relationship("Topic", lazy="selectin")  # noqa: F821
+    workplan: Mapped["Workplan | None"] = relationship("Workplan", lazy="selectin")  # noqa: F821
+    promoted_task: Mapped["Task | None"] = relationship("Task", lazy="selectin")  # noqa: F821
+    notes: Mapped[list["SuggestionNote"]] = relationship(
+        "SuggestionNote",
+        back_populates="suggestion",
+        lazy="selectin",
+        order_by="SuggestionNote.created_at",
+    )
+
+    @property
+    def domain_slug(self) -> str:
+        return self.domain.slug if self.domain is not None else ""
+
+
+class SuggestionNote(Base):
+    __tablename__ = "suggestion_notes"
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=new_uuid)
+    suggestion_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("suggestions.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    stage: 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
+    )
+
+    suggestion: Mapped["Suggestion"] = relationship("Suggestion", back_populates="notes")
+
+
+class SuggestionRelevanceBump(Base):
+    """Audit trail for relevance bumps; supports debounce lookups."""
+
+    __tablename__ = "suggestion_relevance_bumps"
+
+    id: Mapped[uuid.UUID] = mapped_column(UUID(as_uuid=True), primary_key=True, default=new_uuid)
+    suggestion_id: Mapped[uuid.UUID] = mapped_column(
+        UUID(as_uuid=True),
+        ForeignKey("suggestions.id", ondelete="CASCADE"),
+        nullable=False,
+        index=True,
+    )
+    source: Mapped[str] = mapped_column(String(50), nullable=False)
+    source_key: Mapped[str] = mapped_column(String(200), nullable=False)
+    reason: Mapped[str | None] = mapped_column(Text, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(
+        DateTime(timezone=True), server_default=func.now(), nullable=False
+    )