feat: collections, watchlists, and shareable links (v0.9.0)

Phase 3 completion — Personal Workflow feature set is now complete.

Collections / Watchlists:
- New tables: collections (UUID share_token, slug, public/private) and
  collection_bills (unique bill-per-collection constraint)
- Full CRUD API at /api/collections with bill add/remove endpoints
- Public share endpoint /api/collections/share/{token} (no auth)
- /collections list page with inline create form and delete
- /collections/[id] detail page: inline rename, public toggle,
  copy-share-link, bill search/add/remove
- CollectionPicker bookmark-icon popover on bill detail pages
- Collections nav link in sidebar (auth-required)

Shareable Brief Links:
- share_token UUID column on bill_briefs (backfilled on migration)
- Unified public share router at /api/share (brief + collection)
- /share/brief/[token] — minimal layout, full AIBriefCard, CTAs
- /share/collection/[token] — minimal layout, bill list, CTA
- Share2 button in BriefPanel header row, "Link copied!" flash

AuthGuard: /collections → AUTH_REQUIRED; /share prefix → NO_SHELL_PATHS

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

backend/app/models/__init__.py

@@ -1,5 +1,6 @@
 from app.models.bill import Bill, BillAction, BillDocument
 from app.models.brief import BillBrief
+from app.models.collection import Collection, CollectionBill
 from app.models.follow import Follow
 from app.models.member import Member
 from app.models.member_interest import MemberTrendScore, MemberNewsArticle
@@ -17,6 +18,8 @@ __all__ = [
     "BillDocument",
     "BillBrief",
     "BillNote",
+    "Collection",
+    "CollectionBill",
     "Follow",
     "Member",
     "MemberTrendScore",

backend/app/models/brief.py

@@ -1,4 +1,5 @@
 from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, Index
+from sqlalchemy.dialects import postgresql
 from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import relationship
 from sqlalchemy.sql import func
@@ -21,6 +22,7 @@ class BillBrief(Base):
     llm_provider = Column(String(50))
     llm_model = Column(String(100))
     govinfo_url = Column(String, nullable=True)
+    share_token = Column(postgresql.UUID(as_uuid=False), nullable=True, server_default=func.gen_random_uuid())
     created_at = Column(DateTime(timezone=True), server_default=func.now())
 
     bill = relationship("Bill", back_populates="briefs")

backend/app/models/collection.py

@@ -0,0 +1,51 @@
+from sqlalchemy import Boolean, Column, DateTime, ForeignKey, Index, Integer, String, UniqueConstraint
+from sqlalchemy.dialects.postgresql import UUID
+from sqlalchemy.orm import relationship
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class Collection(Base):
+    __tablename__ = "collections"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    user_id = Column(Integer, ForeignKey("users.id", ondelete="CASCADE"), nullable=False)
+    name = Column(String(100), nullable=False)
+    slug = Column(String(120), nullable=False)
+    is_public = Column(Boolean, nullable=False, default=False, server_default="false")
+    share_token = Column(UUID(as_uuid=False), nullable=False, server_default=func.gen_random_uuid())
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
+
+    user = relationship("User", back_populates="collections")
+    collection_bills = relationship(
+        "CollectionBill",
+        cascade="all, delete-orphan",
+        order_by="CollectionBill.added_at.desc()",
+    )
+
+    __table_args__ = (
+        UniqueConstraint("user_id", "slug", name="uq_collections_user_slug"),
+        UniqueConstraint("share_token", name="uq_collections_share_token"),
+        Index("ix_collections_user_id", "user_id"),
+        Index("ix_collections_share_token", "share_token"),
+    )
+
+
+class CollectionBill(Base):
+    __tablename__ = "collection_bills"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    collection_id = Column(Integer, ForeignKey("collections.id", ondelete="CASCADE"), nullable=False)
+    bill_id = Column(String, ForeignKey("bills.bill_id", ondelete="CASCADE"), nullable=False)
+    added_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    collection = relationship("Collection", back_populates="collection_bills")
+    bill = relationship("Bill")
+
+    __table_args__ = (
+        UniqueConstraint("collection_id", "bill_id", name="uq_collection_bills_collection_bill"),
+        Index("ix_collection_bills_collection_id", "collection_id"),
+        Index("ix_collection_bills_bill_id", "bill_id"),
+    )

backend/app/models/user.py

@@ -20,3 +20,4 @@ class User(Base):
     follows = relationship("Follow", back_populates="user", cascade="all, delete-orphan")
     notification_events = relationship("NotificationEvent", back_populates="user", cascade="all, delete-orphan")
     bill_notes = relationship("BillNote", back_populates="user", cascade="all, delete-orphan")
+    collections = relationship("Collection", back_populates="user", cascade="all, delete-orphan")