feat: multi-format capture ingestion (rtl_433, CSV, ZIP) + dedup

Adds src/api/ingest.py and refactors the live upload handler to auto-detect
and route each submission by format instead of assuming .sub:

  - Flipper .sub          -> existing parser + signature matcher (unchanged)
  - rtl_433 .json/.ndjson -> decoded; model is the device (conf 1.0)
  - Wigle-style .csv      -> decoded; one observation per row (conf 0.9)
  - .zip batch            -> recursed; any mix of the above

Also adds stable dedup (SHA256 for whole files, composite key for decoded
records) so re-submissions are skipped rather than stored twice, optional
GPS privacy rounding via manifest privacy_gps_decimals, a session-level GPS
fallback, and helpful errors for unsupported formats. Documented in
docs/SUBMISSION_FORMAT.md with rtl_433/CSV sample fixtures.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/fixtures/ingest_samples/wigle_sample.csv

@@ -0,0 +1,5 @@
+model,manufacturer,frequency,latitude,longitude,timestamp,id,channel
+Chamberlain-Garage,Chamberlain,390000000,34.0201,-118.3011,2026-07-18T12:05:00Z,4471,
+Nexus-TH,Nexus,433920000,34.0215,-118.2994,2026-07-18T12:06:10Z,88,1
+Ford-TPMS,Ford,315000000,34.0189,-118.3040,2026-07-18T12:07:20Z,a19c02,
+Generic-Doorbell,,433920000,34.0230,-118.2971,2026-07-18T12:08:00Z,,