fix: recover from corrupt SQLite database files on startup

[perber]

LeafWiki failed to start after an upgrade if a previous run left a stale SQLite journal file (search.db-journal), causing disk I/O error 3338.

On startup, all four derived SQLite stores (search, links, tags, properties) now detect genuine I/O and corruption errors (SQLITE_IOERR, SQLITE_CORRUPT, SQLITE_NOTADB), delete the database and any sidecar files, and retry initialization once. Since these stores are always rebuilt from the Markdown files on disk, the delete is safe.

Transient errors (SQLITE_BUSY, SQLITE_LOCKED) and resource errors (SQLITE_IOERR_NOMEM) are not treated as recoverable — they are returned immediately without touching the database files.

Shared helpers (IsSQLiteRecoverableError, RemoveSQLiteFiles) live in internal/core/shared/sqliteutil to avoid coupling non-database packages to the SQLite module. The auth stores (users.db, sessions.db) are intentionally excluded from auto-recovery as they hold primary data.

Fixes #1072

[Copilot]

Pull request overview

Recovers from corrupt or stale SQLite database files for the four derived stores (search, links, tags, properties) on startup by detecting a narrow set of recoverable SQLite errors, deleting the DB plus sidecar files (-journal, -wal, -shm), and retrying initialization once. This addresses the upgrade failure in #1072 where a stale search.db-journal produced "disk I/O error (3338)" and prevented startup. The auth stores (users.db, sessions.db) are intentionally left untouched because they hold primary data.

Changes:

• Adds internal/core/shared/sqliteutil with IsSQLiteRecoverableError (matches SQLITE_IOERR=10, SQLITE_CORRUPT=11, SQLITE_NOTADB=26; explicitly excludes SQLITE_IOERR_NOMEM=3082) and RemoveSQLiteFiles.
• Wraps ensureSchema failures in NewSQLiteIndex, NewLinksStore, NewTagsStore, and NewPropertiesStore with a one-shot delete-and-retry recovery path.
• Misc cleanup in internal/search/sqlite_index.go (removes a stray log.Printf per-row in Search, drops unused "log" import).

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
internal/core/shared/sqliteutil/sqlite.go	New shared helpers: classify recoverable SQLite errors and remove DB + sidecar files.
internal/search/sqlite_index.go	Adds recovery around ensureSchema; removes per-row log.Printf and unused import; stray extra blank line.
internal/links/links_store.go	Adds recovery around ensureSchema, resetting s.db and re-Connect-ing on retry.
internal/tags/tags_store.go	Adds recovery: closes db, removes files, reopens and re-runs ensureSchema.
internal/properties/properties_store.go	Adds recovery: closes db, removes files, reopens and re-runs ensureSchema.

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