harden: bound WAL growth — centralize journal_size_limit across all Recall DB writers

[edheltzel]

Recall's main connection (src/db/connection.ts:32-43) sets WAL + busy_timeout but no journal_size_limit (and wal_autocheckpoint is at SQLite default).

BrainLayer documents WAL ballooning to 4.7 GB and fixes it with these PRAGMAs. Red-team caveat: effort is understated — Recall opens DBs directly via new Database() in several places outside getDb():

• hooks/lib/extraction-semaphore.ts
• hooks/RecallExtract.ts
• hooks/RecallStart.ts
• hooks/lib/sqlite-writers.ts

Scope: add a shared pragma helper and apply it at every Recall DB writer, not just src/db/connection.ts.

journal_size_limit is the primary lever; wal_autocheckpoint is already sane at SQLite default. Verified bun:sqlite honors both PRAGMAs.