Add one-shot vs loop sample classification

[LukeMainwaring]

Summary

• Add is_loop boolean field to distinguish one-shot samples (single kicks, snares, chord stabs) from loops (drum patterns, basslines, melodic phrases) — any sample type can be either
• Tiered inference during seeding: filepath keyword matching (word-boundary regex) first, then librosa audio heuristics (duration, onset count, onset regularity) as fallback
• Skip key/BPM computation for one-shots (meaningless for single hits), propagate awareness through agent tools, system prompt, and frontend

Changes

• services/audio_analysis.py: New analyze_and_classify() function that infers loop/one-shot and extracts metadata in a single audio load pass
• models/sample.py: Added is_loop column with server_default, added is_loop filter to search_by_clap()
• schemas/sample.py: is_loop on SampleSchema and SampleSearchRequest
• agents/sample_agent.py: System prompt section on one-shot vs loop behavior rules
• agents/tools/: All three tool files conditionally show key/BPM only for loops; suggest_complement() skips key compatibility for one-shot sources
• routers/samples.py: Pass is_loop filter through search endpoint
• scripts/: All scripts converted to async (use get_async_sqlalchemy_session), shared find_audio_file helper extracted to __init__.py
• core/config.py: Fixed env_file path (was resolving to backend/.env instead of project root), added extra="ignore" for non-Settings env vars
• pyproject.toml: Added sqlalchemy[asyncio] extra (provides greenlet)
• Frontend: One-shot/loop badge on sample cards, segmented filter toggle (All/One-shots/Loops) above type filters
• Migration: c1e3a6c19709_add_is_loop_column

Test Plan

• Run uv run seed-db — verify one-shots get key=None, bpm=None; loops get full metadata
• Verify filepath keyword inference (samples in "one-shot" dirs → is_loop=False, "loop" dirs → is_loop=True)
• Hit GET /api/samples — verify is_loop appears in response
• Ask agent to analyze a one-shot — should show "Category: one-shot" with no key/BPM
• Ask agent to analyze a loop — should show "Category: loop" with key/BPM
• Test frontend one-shot/loop filter toggle and badge display
• Run uv run pre-commit run --all-files and cd frontend && pnpm lint

🤖 Generated with Claude Code