feat: add Tower Log narrative event feed (Fixes #7)

Adds the tower_log DB table, a narrateEvent method on AgentService (Haiku-powered, stub-safe), a tower-log service that persists and broadcasts entries, a GET /api/tower-log REST endpoint, WebSocket bootstrap and real-time push, and a bottom-sheet Tower Log panel in the-matrix UI with fade-in animations and auto-scroll.

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

lib/db/migrations/0010_tower_log.sql

@@ -0,0 +1,15 @@
+-- Migration: Tower Log narrative event feed (#7)
+-- Adds the tower_log table that stores prose narrative entries about
+-- Workshop activity, generated by Haiku on key events.
+
+CREATE TABLE IF NOT EXISTS tower_log (
+  id          TEXT PRIMARY KEY,
+  narrative   TEXT NOT NULL,
+  event_type  TEXT NOT NULL,
+  agent_id    TEXT,
+  job_id      TEXT,
+  created_at  TIMESTAMPTZ NOT NULL DEFAULT NOW()
+);
+
+CREATE INDEX IF NOT EXISTS idx_tower_log_created_at
+  ON tower_log(created_at DESC);