db+game: tech table + starting tech list seeded on new game and v5 backfill step

lib/db/client.ts

@@ -81,6 +81,19 @@ CREATE TABLE IF NOT EXISTS ship_systems (
   UNIQUE (save_id, type)
 );
 
+CREATE TABLE IF NOT EXISTS tech (
+  id INTEGER PRIMARY KEY AUTOINCREMENT,
+  save_id INTEGER NOT NULL REFERENCES saves(id),
+  slug TEXT NOT NULL, -- stable key, e.g. WEAPONS_SYSTEMS
+  name TEXT NOT NULL, -- display name, e.g. 'WEAPONS SYSTEMS'
+  cost_kind TEXT NOT NULL, -- 'resource' | 'part'
+  cost_qty INTEGER NOT NULL DEFAULT 1,
+  prerequisites TEXT NOT NULL DEFAULT '', -- comma-separated tech slugs, '' when none
+  effect TEXT NOT NULL, -- effect slug — semantics in EFFECTS (lib/game/tech.ts)
+  researched INTEGER NOT NULL DEFAULT 0,
+  UNIQUE (save_id, slug)
+);
+
 CREATE TABLE IF NOT EXISTS events (
   id INTEGER PRIMARY KEY AUTOINCREMENT,
   save_id INTEGER NOT NULL REFERENCES saves(id),