feat: add memory_type to FTS5 index for keyword search

[ajianaz]

Summary

memories_fts FTS5 only indexes: content, tags, namespace. The memory_type column is not indexed.

Current:

CREATE VIRTUAL TABLE memories_fts USING fts5(content, tags, namespace, content='memories');

Proposed

Add memory_type to FTS5 columns and update triggers.

Acceptance Criteria

Functional

• Add memory_type to FTS5 columns
• Update FTS5 triggers to include memory_type
• Rebuild existing FTS5 index

Verification (CMO can run without reading code)

• sqlite3 uteke.db "SELECT * FROM memories_fts WHERE memories_fts MATCH 'memory_type:decision'" → returns decision-type memories
• sqlite3 uteke.db "SELECT * FROM memories_fts WHERE memories_fts MATCH 'memory_type:event'" → returns event-type memories
• sqlite3 uteke.db "SELECT * FROM memories_fts WHERE memories_fts MATCH 'memory_type:fact'" → returns fact-type memories (most common)
• After inserting new memory with type=insight → FTS5 query finds it
• Query time < 1ms for memory_type filter on 17K rows

Tests

• Integration: rebuild FTS5 → all 17K+ memories indexed correctly
• Unit: insert → FTS5 contains new row

Priority

Low — /query endpoint (#657) is the primary solution.

Dependencies

Coordinate with #656 (index creation).

[ajianaz]

Dependencies

Coordinate with #656 (index creation) to batch schema migration.