fix(sync): batch inserts + normalize nulls to avoid SQLite param mismatch

- Batch repository inserts with dynamic sizing under SQLite 999-param limit
- Normalize undefined → null to keep multi-row insert shapes consistent
- De-duplicate owned + starred repos by fullName (prefer starred variant)
- Enforce uniqueness via (user_id, full_name) + onConflictDoNothing
- Handle starred name collisions (suffix/prefix) across mirror + metadata
- Add repo-utils helpers + tests; guard Octokit.plugin in tests
- Remove manual unique index from entrypoint; rely on drizzle-kit migrations

drizzle/0005_polite_preak.sql

@@ -0,0 +1 @@
+CREATE UNIQUE INDEX `uniq_repositories_user_full_name` ON `repositories` (`user_id`,`full_name`);

drizzle/meta/_journal.json

@@ -36,6 +36,13 @@
       "when": 1757392620734,
       "tag": "0004_grey_butterfly",
       "breakpoints": true
+    },
+    {
+      "idx": 5,
+      "version": "6",
+      "when": 1757786449446,
+      "tag": "0005_polite_preak",
+      "breakpoints": true
     }
   ]
 }