fix: resolve remaining CI failures — mapper FK mismatch and lint errors

Backend: Use string-form foreign_keys on SessionBranch.session to match
AISession.branches — mixed column-object vs string-expression caused
SQLAlchemy mapper initialization conflict.

Frontend lint fixes:
- Remove unused _escalateUploads, _intakeUploads destructured vars
- Remove unused _ticket, _chatId, _pinned parameters
- Replace empty interface with type alias (public-templates.ts)
- Suppress setState-in-effect in SimilarSessions, SidebarStatsBar,
  FlowPilotAnalyticsPage (intentional prop sync patterns)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/app/models/session_branch.py

@@ -51,7 +51,7 @@ class SessionBranch(Base):
     updated_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=lambda: datetime.now(timezone.utc), onupdate=lambda: datetime.now(timezone.utc))
 
     # Relationships
-    session: Mapped["AISession"] = relationship("AISession", foreign_keys=[session_id], back_populates="branches")
+    session: Mapped["AISession"] = relationship("AISession", foreign_keys="[SessionBranch.session_id]", back_populates="branches")
     parent_branch: Mapped[Optional["SessionBranch"]] = relationship("SessionBranch", remote_side="SessionBranch.id", foreign_keys=[parent_branch_id])
     fork_point_step: Mapped[Optional["AISessionStep"]] = relationship("AISessionStep", foreign_keys=[fork_point_step_id])
     status_changed_by_user: Mapped[Optional["User"]] = relationship("User", foreign_keys=[status_changed_by])