refactor(store): swap mattn/go-sqlite3 for modernc.org/sqlite

Pure-Go SQLite driver — no CGO, no C compiler. Enables:
- static binaries (verified: `file` shows statically linked)
- cross-compile to linux/arm64, darwin/amd64+arm64, windows/amd64+arm64
- goreleaser now builds 6 OS/arch targets + windows .zip
- Dockerfile drops gcc/musl-dev, sets CGO_ENABLED=0
- release-binaries drops gcc/musl-dev

Driver name changes sqlite3 → sqlite, DSN pragmas use
_pragma=name(value) format. All tests pass CGO=0 and CGO=1 -race.

Homebrew cask block removed (was skip_upload:true dead config).

.gitea/workflows/release-binaries.yml

@@ -13,7 +13,7 @@ jobs:
         shell: sh
     steps:
       - name: Install build tools
-        run: apk add --no-cache git gcc musl-dev
+        run: apk add --no-cache git
 
       - uses: actions/checkout@v4
         with: