Round 7a: per-operator outbound attribution + GDELT GCS-direct fix (#292)

== Per-install operator handle for every third-party API call ==

Before this PR, every Shadowbroker install identified itself to
Wikipedia, Wikidata, Nominatim, GDELT, OpenMHz, Broadcastify,
weather.gov, NUFORC, Sentinel/Planetary Computer, TinyGS / CelesTrak,
Shodan, Finnhub, and others with a single project-wide User-Agent
("Shadowbroker/1.0" or "ShadowBroker-OSINT/1.0"). From the upstream's
perspective every install in the world looked like one giant scraper.
If one install misbehaved, the upstream's only recourse was to block
"Shadowbroker" as a whole.

PR #284 inadvertently doubled down on this in the frontend by
introducing a shared `WIKIMEDIA_API_USER_AGENT` constant. This PR
retrofits both backends to per-operator attribution.

  New setting: OPERATOR_HANDLE (env var / settings UI / auto-gen)
  New helper:  network_utils.outbound_user_agent("purpose")

The handle is auto-generated as "operator-XXXXXX" on first call (the
"shadow-" prefix from earlier drafts was deliberately dropped — too
suspicious-looking for abuse-detection systems). Operators can
override via OPERATOR_HANDLE; the value is sanitized to lowercase
alphanumeric+dash+underscore and capped at 48 chars. Persisted to
backend/data/operator_handle.json so it survives container restarts.

Retrofitted call sites (every previously-MONSTER User-Agent):
  - services/region_dossier.py (Wikipedia + Wikidata + Nominatim)
  - services/geocode.py         (Nominatim)
  - services/sentinel_search.py (Microsoft Planetary Computer)
  - services/feed_ingester.py   (operator-curated RSS feeds)
  - services/fetchers/earth_observation.py (weather.gov, NUFORC)
  - services/fetchers/infrastructure.py
  - services/fetchers/aircraft_database.py
  - services/fetchers/route_database.py
  - services/fetchers/trains.py
  - services/fetchers/meshtastic_map.py
  - services/shodan_connector.py
  - services/unusual_whales_connector.py (Finnhub)
  - services/tinygs_fetcher.py            (CelesTrak + TinyGS)
  - services/sar/sar_products_client.py
  - services/geopolitics.py               (GDELT)
  - services/radio_intercept.py           (Broadcastify + OpenMHz)
  - routers/cctv.py + main.py             (CCTV proxy)
  - routers/ai_intel.py
  - scripts/convert_power_plants.py       (release-time data refresh)

Spoofed browser UAs removed (issues #289 / #290 / #291 — tg12 audit):
  - cloudscraper-based Chrome impersonation against api.openmhz.com
    -> replaced with honest requests + per-install UA
  - Mozilla/5.0 spoofed UA on Broadcastify scrape
    -> replaced with honest UA
  - Mozilla/5.0 + fake first-party Referer on OpenMHz audio relay
    -> replaced with honest UA
  - cloudscraper dependency dropped from pyproject.toml + uv.lock

Frontend retrofit:
  - new GET /api/settings/operator-handle endpoint (local-operator
    gated) returns the install's handle
  - frontend/src/lib/wikimediaClient.ts fetches the handle once on
    first use, caches it for page lifetime, embeds it in the
    Api-User-Agent for every Wikipedia / Wikidata browser-direct call

== GDELT GCS-direct fix ==

GDELT's data.gdeltproject.org is a CNAME to a Google Cloud Storage
bucket. GCS responds with the wildcard *.storage.googleapis.com cert
which legitimately does NOT cover the GDELT custom domain, so Python's
TLS verification correctly refuses the connection. Some networks
happen to route through a path where this works; many (notably Docker
Desktop's outbound NAT on local installs) do not. Verified on the
maintainer's local install: GDELT was unreachable; 1610 geopolitical
events / 48 export files were dropping silently.

Fix: services/geopolitics._gcs_direct_gdelt_url() rewrites any
data.gdeltproject.org URL to its GCS-direct equivalent
(storage.googleapis.com/data.gdeltproject.org/...) where the standard
GCS cert is genuinely valid. api.gdeltproject.org and every other host
are left untouched.

Confirmed live: backend log goes from
  GDELT lastupdate failed: 500
to
  Downloading 48 GDELT export files...
  Downloaded 48/48 GDELT exports
  GDELT parsed: 1610 conflict locations from 48 files

== Tests ==

  backend/tests/test_per_operator_outbound_attribution.py (12 tests)
  backend/tests/test_gdelt_gcs_direct_rewrite.py          (6 tests)
  backend/tests/test_region_dossier_wikimedia_ua.py       (updated to
    pin the helper + per-operator handle, not the old constant)
  frontend/src/__tests__/utils/wikimediaClient.test.ts    (rewritten
    to mock /api/settings/operator-handle and assert per-operator UA)

Local: backend 114/114 security+audit+round7a suite green;
       frontend 718/718 vitest suite green.

Credit: tg12 (external security audit, issues #289/#290/#291
relating to spoofed UAs); BigBodyCobain (operator-prefix call,
GDELT cloud-vs-local diagnosis).

backend/services/config.py

@@ -295,6 +295,19 @@ class Settings(BaseSettings):
     # service operator can identify per-install traffic instead of a generic
     # "ShadowBroker" aggregate.
     MESHTASTIC_OPERATOR_CALLSIGN: str = ""
+    # Per-install operator handle used in the User-Agent for EVERY third-party
+    # API the backend calls (Wikipedia, Wikidata, Nominatim, GDELT, OpenMHz,
+    # Broadcastify, weather.gov, NUFORC, etc.). The default is empty, in which
+    # case backend/services/network_utils.py auto-generates a stable
+    # pseudonymous handle like "operator-7f3a92" on first use and caches it.
+    # Operators who want to identify themselves with a real handle can set
+    # this; operators who want to stay pseudonymous can leave it empty.
+    #
+    # The handle is sent ONLY to public third-party APIs. It is NEVER mixed
+    # into mesh / Wormhole / Infonet identity (those have their own crypto
+    # identity layer; conflating the two would leak public attribution into
+    # private mesh state).
+    OPERATOR_HANDLE: str = ""
 
     # SAR (Synthetic Aperture Radar) data layer
     # Mode A — free catalog metadata, no account, default-on