fix(deps): bump better-sqlite3 to ^12.10.0 for Node.js 26 compatibility

[jelloeater-agent]

What

Bumps better-sqlite3 from ^11.7.0 to ^12.10.0 and raises the minimum Node version from >=18 to >=20.

Why

better-sqlite3 v11.x relies on three V8 C++ APIs (GetPrototype, GetIsolate, PropertyCallbackInfo::This) that were removed in V8 14.6, which ships with Node.js 26. Since there are no prebuilt binaries for Node 26, npm falls back to compilation — which fails with hard errors on macOS and anywhere without a matching prebuilt:

./src/util/binder.lzz:40: error: no member named 'GetPrototype' in 'v8::Object'
./src/better_sqlite3.lzz:68: error: no member named 'GetIsolate' in 'v8::Context'
./src/objects/database.lzz:416: error: no member named 'This' in 'v8::PropertyCallbackInfo<v8::Value>'

Version 12.10.0 is the first release with Node 26 prebuilt binaries (PR #1468) and uses the updated V8 APIs.

Impact

• JS API is unchanged — .prepare(), .run(), .get(), .all(), .exec() all work identically. Zero code changes needed.
• Node 18 has been EOL since April 2025, so the engines bump is appropriate.
• This is the only native addon in the project; no other compatibility concerns.