feat(knowledge-flywheel): add Phase 3 Knowledge Flywheel — AI analysis, review queue, analytics

Phase 3 implementation:
- AI session analysis service that generates flow proposals from resolved sessions
- APScheduler job for batch processing pending analyses (max_instances=1)
- Knowledge gap detection (weak options, high escalation signals)
- Flow proposals CRUD with team admin review workflow (approve/edit/dismiss/reject)
- FlowPilot analytics dashboard with confidence tiers, PSA metrics, knowledge gaps
- In-session script generator component
- Review queue page with filtering and proposal detail panel

Bug fixes from review (12 total):
- Fix "Edit & Publish" navigating to non-existent /editor/new route
- Hide Approve button for enhancement proposals (require Edit & Publish)
- Add max_instances=1 to scheduler to prevent TOCTOU race
- Fix eventual_success case() double-counting failed retries
- Add tree_structure validation before creating tree from proposal
- Simplify script generator rendering condition
- Add severity style fallback, toFixed on rates, Link instead of <a href>
- Add toast.warning on dismiss failure, fix dedup for domain-less sessions
- Cast Decimal to int in knowledge gap evidence dicts

Also updates CLAUDE.md with lessons 67-71 and Phase 3 project structure.

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

backend/app/schemas/flow_proposal.py

@@ -0,0 +1,51 @@
+"""Pydantic schemas for flow proposals (Knowledge Flywheel / Review Queue)."""
+from __future__ import annotations
+
+from typing import Optional, Any
+from uuid import UUID
+from datetime import datetime
+
+from pydantic import BaseModel, Field
+
+
+class FlowProposalSummary(BaseModel):
+    """Compact proposal for list views."""
+    id: UUID
+    proposal_type: str
+    title: str
+    description: str | None = None
+    problem_domain: str | None = None
+    confidence_score: float
+    supporting_session_count: int
+    status: str
+    target_flow_id: UUID | None = None
+    source_session_id: UUID
+    created_at: datetime
+
+    model_config = {"from_attributes": True}
+
+
+class FlowProposalDetail(FlowProposalSummary):
+    """Full proposal detail with flow data."""
+    proposed_flow_data: dict[str, Any]
+    proposed_diff: dict[str, Any] | None = None
+    supporting_session_ids: list[str] = []
+    reviewer_notes: str | None = None
+    reviewed_by: UUID | None = None
+    reviewed_at: datetime | None = None
+
+
+class ReviewProposalRequest(BaseModel):
+    """Review action on a proposal."""
+    action: str = Field(..., pattern="^(approve|reject|modify|dismiss)$")
+    reviewer_notes: str | None = None
+    modified_flow_data: dict[str, Any] | None = None  # Only for "modify"
+
+
+class FlowProposalStats(BaseModel):
+    """Dashboard stats for the review queue."""
+    pending_count: int
+    approved_this_week: int
+    rejected_this_week: int
+    auto_reinforced_this_week: int
+    top_domains: list[dict[str, Any]] = []  # [{domain, count}]