ci: restructure pipeline — sequential fail-fast, Go server E2E, remove deprecated JS tests (#256)

## Summary

Complete CI pipeline restructure. Sequential fail-fast chain, E2E tests
against Go server with real staging data, all deprecated Node.js server
tests removed.

### Pipeline (PR):
1. **Go unit tests** — fail-fast, coverage + badges
2. **Playwright E2E** — against Go server with fixture DB, frontend
coverage, fail-fast on first failure
3. **Docker build** — verify containers build

### Pipeline (master merge):
Same chain + deploy to staging + badge publishing

### Removed:
- All Node.js server-side unit tests (deprecated JS server)
- `npm ci` / `npm run test` steps
- JS server coverage collection (`COVERAGE=1 node server.js`)
- Changed-files detection logic
- Docs-only CI skip logic
- Cancel-workflow API hacks

### Added:
- `test-fixtures/e2e-fixture.db` — real data from staging (200 nodes, 31
observers, 500 packets)
- `scripts/capture-fixture.sh` — refresh fixture from staging API
- Go server launches with `-port 13581 -db test-fixtures/e2e-fixture.db
-public public-instrumented`

---------

Co-authored-by: Kpa-clawbot <kpabap+clawdbot@gmail.com>
Co-authored-by: you <you@example.com>

scripts/capture-fixture.sh

@@ -0,0 +1,142 @@
+#!/bin/bash
+# Capture a fixture DB from staging for E2E tests
+# Usage: ./scripts/capture-fixture.sh [source_url]
+#
+# Downloads nodes, observers, and recent packets from the staging API
+# and creates a SQLite database suitable for E2E testing.
+
+set -e
+
+SOURCE_URL="${1:-https://analyzer.00id.net}"
+DB_PATH="test-fixtures/e2e-fixture.db"
+
+echo "Capturing fixture from $SOURCE_URL..."
+
+mkdir -p test-fixtures
+rm -f "$DB_PATH"
+
+# Create schema
+sqlite3 "$DB_PATH" <<'SQL'
+CREATE TABLE nodes (
+    public_key TEXT PRIMARY KEY,
+    name TEXT,
+    role TEXT,
+    lat REAL,
+    lon REAL,
+    last_seen TEXT,
+    first_seen TEXT,
+    advert_count INTEGER DEFAULT 0,
+    battery_mv INTEGER,
+    temperature_c REAL
+);
+
+CREATE TABLE observers (
+    id TEXT PRIMARY KEY,
+    name TEXT,
+    iata TEXT,
+    last_seen TEXT,
+    first_seen TEXT,
+    packet_count INTEGER DEFAULT 0,
+    model TEXT,
+    firmware TEXT,
+    client_version TEXT,
+    radio TEXT,
+    battery_mv INTEGER,
+    uptime_secs INTEGER,
+    noise_floor REAL
+);
+
+CREATE TABLE transmissions (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    raw_hex TEXT NOT NULL,
+    hash TEXT NOT NULL UNIQUE,
+    first_seen TEXT NOT NULL,
+    route_type INTEGER,
+    payload_type INTEGER,
+    payload_version INTEGER,
+    decoded_json TEXT,
+    created_at TEXT DEFAULT (datetime('now'))
+);
+
+CREATE TABLE observations (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    transmission_id INTEGER NOT NULL REFERENCES transmissions(id),
+    observer_idx INTEGER,
+    direction TEXT,
+    snr REAL,
+    rssi REAL,
+    score INTEGER,
+    path_json TEXT,
+    timestamp INTEGER NOT NULL
+);
+SQL
+
+# Fetch nodes
+echo "Fetching nodes..."
+curl -sf "$SOURCE_URL/api/nodes?limit=200" | python3 -c "
+import json, sys, sqlite3
+data = json.load(sys.stdin)
+nodes = data.get('nodes', data) if isinstance(data, dict) else data
+db = sqlite3.connect('$DB_PATH')
+for n in nodes[:200]:
+    db.execute('INSERT OR IGNORE INTO nodes VALUES (?,?,?,?,?,?,?,?,?,?)',
+        (n.get('public_key',''), n.get('name',''), n.get('role',''),
+         n.get('lat'), n.get('lon'), n.get('last_seen',''), n.get('first_seen',''),
+         n.get('advert_count',0), n.get('battery_mv'), n.get('temperature_c')))
+db.commit()
+print(f'  Inserted {min(len(nodes), 200)} nodes')
+db.close()
+"
+
+# Fetch observers
+echo "Fetching observers..."
+curl -sf "$SOURCE_URL/api/observers" | python3 -c "
+import json, sys, sqlite3
+data = json.load(sys.stdin)
+observers = data.get('observers', data) if isinstance(data, dict) else data
+db = sqlite3.connect('$DB_PATH')
+for o in observers:
+    db.execute('INSERT OR IGNORE INTO observers VALUES (?,?,?,?,?,?,?,?,?,?,?,?,?)',
+        (o.get('id',''), o.get('name',''), o.get('iata',''),
+         o.get('last_seen',''), o.get('first_seen',''),
+         o.get('packet_count',0), o.get('model',''), o.get('firmware',''),
+         o.get('client_version',''), o.get('radio',''),
+         o.get('battery_mv'), o.get('uptime_secs'), o.get('noise_floor')))
+db.commit()
+print(f'  Inserted {len(observers)} observers')
+db.close()
+"
+
+# Fetch recent packets
+echo "Fetching recent packets..."
+curl -sf "$SOURCE_URL/api/packets?limit=500" | python3 -c "
+import json, sys, sqlite3
+data = json.load(sys.stdin)
+packets = data.get('packets', data) if isinstance(data, dict) else data
+db = sqlite3.connect('$DB_PATH')
+for p in packets:
+    try:
+        cur = db.execute('INSERT OR IGNORE INTO transmissions (raw_hex, hash, first_seen, route_type, payload_type, payload_version, decoded_json) VALUES (?,?,?,?,?,?,?)',
+            (p.get('raw_hex',''), p.get('hash',''), p.get('first_seen',''),
+             p.get('route_type'), p.get('payload_type'), p.get('payload_version'),
+             p.get('decoded_json')))
+        tid = cur.lastrowid
+        if tid and p.get('observer_id'):
+            db.execute('INSERT INTO observations (transmission_id, observer_idx, direction, snr, rssi, score, path_json, timestamp) VALUES (?,?,?,?,?,?,?,?)',
+                (tid, p.get('observer_id'), p.get('direction'),
+                 p.get('snr'), p.get('rssi'), None,
+                 p.get('path_json'),
+                 int(p.get('timestamp','0')) if p.get('timestamp','').isdigit() else 0))
+    except Exception as e:
+        pass  # Skip duplicates
+db.commit()
+print(f'  Inserted {len(packets)} transmissions')
+db.close()
+"
+
+SIZE=$(du -h "$DB_PATH" | cut -f1)
+echo "✅ Fixture DB created: $DB_PATH ($SIZE)"
+echo "   Nodes: $(sqlite3 "$DB_PATH" 'SELECT COUNT(*) FROM nodes')"
+echo "   Observers: $(sqlite3 "$DB_PATH" 'SELECT COUNT(*) FROM observers')"
+echo "   Transmissions: $(sqlite3 "$DB_PATH" 'SELECT COUNT(*) FROM transmissions')"
+echo "   Observations: $(sqlite3 "$DB_PATH" 'SELECT COUNT(*) FROM observations')"