migrate to SQLite and prepare for MCP deployment

Switch from PostgreSQL to SQLite (modernc.org/sqlite, pure Go) for
simpler deployment on the MCP platform. Fix URL normalization to
preserve query parameters so sites like YouTube deduplicate correctly.
Add Dockerfile, Makefile, and MCP service definition. Add pg2sqlite
migration tool. Support $PORT env var for MCP port assignment.

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

schema.sql

@@ -1,7 +1,7 @@
-CREATE TABLE urls (
-        id              UUID PRIMARY KEY DEFAULT gen_random_uuid(),
-	url		TEXT NOT NULL,
-	nurl		TEXT NOT NULL, -- normalized url
-	short		TEXT NOT NULL UNIQUE,
-	created_at	TIMESTAMPTZ NOT NULL DEFAULT NOW()
+CREATE TABLE IF NOT EXISTS urls (
+	id         TEXT PRIMARY KEY,
+	url        TEXT NOT NULL,
+	nurl       TEXT NOT NULL,
+	short      TEXT NOT NULL UNIQUE,
+	created_at TEXT NOT NULL
 );