feat(pitch-deck): full pitch versioning with git-style history (#4)

Full pitch versioning: 12 data tables versioned as JSONB snapshots,
git-style parent chain (draft→commit→fork), per-investor assignment,
side-by-side diff engine, version-aware /api/data + /api/financial-model.

Bug fixes: FM editor [object Object] for JSONB arrays, admin scroll.

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

pitch-deck/migrations/003_pitch_versions.sql

@@ -0,0 +1,36 @@
+-- =========================================================
+-- Pitch Deck: Version Management (Git-Style History)
+-- =========================================================
+
+-- Version metadata: each version points to its parent (git-style DAG)
+CREATE TABLE IF NOT EXISTS pitch_versions (
+  id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  name          TEXT NOT NULL,
+  description   TEXT,
+  parent_id     UUID REFERENCES pitch_versions(id) ON DELETE SET NULL,
+  status        VARCHAR(20) NOT NULL DEFAULT 'draft'
+                CHECK (status IN ('draft', 'committed')),
+  created_by    UUID REFERENCES pitch_admins(id) ON DELETE SET NULL,
+  committed_at  TIMESTAMPTZ,
+  created_at    TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+CREATE INDEX IF NOT EXISTS idx_pitch_versions_parent ON pitch_versions(parent_id);
+CREATE INDEX IF NOT EXISTS idx_pitch_versions_status ON pitch_versions(status);
+
+-- Version content: one row per data table per version (fully materialized)
+-- table_name values: company, team, financials, market, competitors, features,
+--   milestones, metrics, funding, products, fm_scenarios, fm_assumptions
+CREATE TABLE IF NOT EXISTS pitch_version_data (
+  id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+  version_id    UUID NOT NULL REFERENCES pitch_versions(id) ON DELETE CASCADE,
+  table_name    TEXT NOT NULL,
+  data          JSONB NOT NULL,
+  updated_at    TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+  updated_by    UUID REFERENCES pitch_admins(id) ON DELETE SET NULL,
+  UNIQUE(version_id, table_name)
+);
+CREATE INDEX IF NOT EXISTS idx_pitch_version_data_version ON pitch_version_data(version_id);
+
+-- Per-investor version assignment (NULL = use base tables)
+ALTER TABLE pitch_investors
+  ADD COLUMN IF NOT EXISTS assigned_version_id UUID REFERENCES pitch_versions(id) ON DELETE SET NULL;