add-session-cardlisted

# Add Session Analytics Card Add a new analytics card to the session summary panel following the card-per-table architecture. ## Overview The analytics system uses a **card-per-table** architecture where each card type has: - Its own database table (`session_card_<name>`) - Independent version constant for cache invalidation - An **analyzer** that extracts metrics from a `FileCollection` - Frontend component registered in the card registry ## Instructions for Claude Use **TodoWrite** to track all phases. This is a multi-step task requiring both backend and frontend changes. ### Phase 1: Plan the Card Before writing any code: - [ ] Understand what metrics the card will display - [ ] Identify which transcript line types contain the data - [ ] Plan the database schema (what columns are needed) - [ ] Plan the API response format ### Phase 2: Backend - Database Migration Create migration files in `backend/internal/db/migrations/`: **Up migration** (`000XXX_session_card_<name>.up.sql`): ```sql CREATE TABLE session_card_<name> ( session_id UUID PRIMARY KEY REFERENCES sessions(id) ON DELETE CASCADE, version INT NOT NULL DEFAULT 1, computed_at TIMESTAMPTZ NOT NULL, up_to_line BIGINT NOT NULL, -- card-specific columns (use snake_case) my_metric BIGINT NOT NULL DEFAULT 0 ); CREATE INDEX idx_session_card_<name>_version ON session_card_<name>(version); ``` **Down migration** (`000XXX_session_card_<name>.down.sql`): ```sql DROP TABLE IF EXISTS session_c