refactor: API server modularization - route modules, extracted services; dashboard spectrogram end-of-clip fix

Content snapshot of dev (f524937..ad9191a):

- api.py shrinks from ~4,700 lines to a slim composition root: routes
  move into core/routes/ (auth, settings, system, migration, media,
  images, species, observations, detections) and shared logic into
  focused services (api_infra, bird_image_service, detection_presenter,
  settings_store, update_service)
- Logging is configured before the import-time DatabaseManager
  construction so its startup messages reach the configured handlers
- Dashboard call player: the rolling spectrogram no longer scrolls a
  strip of blank columns in at the right edge when playback ends — a
  digital-silence gate on the analyser's raw waveform stops the scroll
  exactly when the signal ends

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WqhLxxU3aSJcRAHLJSLs2p

Author: Suncuss

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## [Unreleased]
 
+- Fixed the dashboard call player's rolling spectrogram scrolling a strip of blank columns in at the right edge when playback ended — the display now stops together with the audio
 - Added a per-species summary table maintained alongside every detection, replacing repeated full-history scans as the source for species facts. It verifies itself at startup and rebuilds automatically if anything drifts
 - Improved the heaviest species queries by serving them from the new summary table: the dashboard's recent-unique-species list drops from up to seconds on busy stations to ~1ms (this was a known cause of intermittent dashboard timeouts), the species catalog and gallery load in ~1ms instead of scanning the full detection history, and the species detail card computes about twice as fast
 - Improved species detail chart loading: the per-species distribution queries now use an indexed time-range scan instead of examining every detection of the species per chart view — up to 7x faster on frequently detected species, most noticeable on low-power devices