Fix over-correlation: geocoding precision, thin path ambiguity, skip_reason propagation

- Geocoding: reject GEOMETRIC_CENTER/APPROXIMATE results — vague location strings
  (regions, city centroids) were resolving to node-area coords and creating false
  proximity matches that merged unrelated incidents
- Thin path: on dispatch channels with multiple active incidents, skip attachment
  rather than guessing — "10-4" with 3 active incidents is genuinely ambiguous
- Short transcripts (≤5 words) now write skip_reason="transcript_too_short" to
  the call doc, matching garbage transcript behavior
- upload.py no-scenes fallback now checks skip_reason before running correlation —
  flagged calls (garbage, too short) no longer attach via thin path
- Update Server README to reflect current project purpose, goals, and pipeline

drb-c2-core/app/routers/upload.py

@@ -241,20 +241,24 @@ async def _run_intelligence_pipeline(
 
         # Correlator also runs for calls with no scenes (unclassified) to attempt
         # talkgroup-based linking even when no transcript could be produced.
+        # Skip when extraction flagged the call — garbage or too-short transcripts
+        # carry no signal and would only attach spuriously via the thin path.
         if not scenes:
-            incident_id = await incident_correlator.correlate_call(
-                call_id=call_id,
-                node_id=node_id,
-                system_id=system_id,
-                talkgroup_id=talkgroup_id,
-                talkgroup_name=talkgroup_name,
-                tags=[],
-                incident_type=None,
-                location=None,
-                location_coords=None,
-            )
-            if incident_id:
-                incident_ids.append(incident_id)
+            _call_doc = await fstore.doc_get("calls", call_id)
+            if not (_call_doc or {}).get("skip_reason"):
+                incident_id = await incident_correlator.correlate_call(
+                    call_id=call_id,
+                    node_id=node_id,
+                    system_id=system_id,
+                    talkgroup_id=talkgroup_id,
+                    talkgroup_name=talkgroup_name,
+                    tags=[],
+                    incident_type=None,
+                    location=None,
+                    location_coords=None,
+                )
+                if incident_id:
+                    incident_ids.append(incident_id)
 
     if incident_ids:
         await fstore.doc_set("calls", call_id, {"incident_ids": incident_ids})