feat: node26 image using built-in node:sqlite (drop native toolchain)

[jtrotsky]

Moves the FreeBSD Papra image to node26 (matching upstream's .nvmrc) and replaces the better-sqlite3 driver swap with node26's built-in node:sqlite, driven through drizzle-orm/sqlite-proxy. This removes the entire C toolchain from the builder (no FreeBSD-clang/lld/toolchain/clibs-dev, no node-gyp, python, gmake) -- there is no native addon to compile -- and decouples the DB layer from node ABI churn (the better-sqlite3 11->12 break on node26 was exactly this class of problem).

node26 specifics:

• node26 ships only in FreeBSD's latest pkg branch (the base image points at quarterly, which tops out at node25), so switch the branch before install in both stages.
• papra uses the TC39 Temporal global. Official node26 ships it built-in, but FreeBSD's node26 package is compiled WITHOUT it (and --harmony-temporal is a no-op here), so preload a spec-compliant polyfill via node --import temporal-polyfill/global.

database.ts maps node:sqlite to the libsql semantics papra expects:

• sqlite-proxy callback uses StatementSync.setReturnArrays(true) for the positional rows drizzle's query builder wants.
• attachBatch: custom db.batch (sqlite-proxy's native batch can't handle papra's eagerly-executed db.run() results).
• attachLibsqlRaw: raw db.run/all/get return libsql's row OBJECTS (migrations 0010-0019 read db.run(...).rows; the health check reads db.all(...)).

The other three FreeBSD patches (health-check, tasks-driver, migration 0006) are unchanged. Remote libSQL/Turso URLs remain unsupported (local file DB only) -- same as before.