feat: inspector page, link debug enhancements, security hardening

- Add /inspector page: visual model-accurate switch chassis diagrams
  (USF5P, USL8A, US24PRO, USPPDUP, USMINI), clickable port blocks
  with color coding (green=up, amber=PoE, cyan=uplink, grey=down),
  detail panel with stats/PoE/LLDP, LLDP-based path debug side-by-side

- Link Debug: port number badges (#N), LLDP neighbor line, PoE class/max,
  collapsible host/switch panels with sessionStorage persistence

- monitor.py: collect LLDP neighbor map + PoE class/max/mode per switch
  port; PulseClient uses requests.Session() for HTTP keep-alive; add
  shlex.quote() around interface names (defense-in-depth)

- Security: suppress buttons use data-* attrs + delegated click handler
  instead of inline onclick with Jinja2 variable interpolation; remove
  | safe filter from user-controlled fields in suppressions.html;
  setDuration() takes explicit el param instead of implicit event global

- db.py: thread-local connection reuse with ping(reconnect=True) to
  avoid a new TCP handshake per query

- .gitignore: add config.json (contains credentials), __pycache__

- README: full rewrite covering architecture, all 4 pages, alert logic,
  config reference, deployment, troubleshooting, security notes

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

templates/suppressions.html

@@ -50,11 +50,11 @@
         <div class="form-group">
           <label>Duration</label>
           <div class="duration-pills">
-            <button type="button" class="pill" onclick="setDur(30)">30 min</button>
-            <button type="button" class="pill" onclick="setDur(60)">1 hr</button>
-            <button type="button" class="pill" onclick="setDur(240)">4 hr</button>
-            <button type="button" class="pill" onclick="setDur(480)">8 hr</button>
-            <button type="button" class="pill pill-manual active" onclick="setDur(null)">Manual ∞</button>
+            <button type="button" class="pill" onclick="setDur(30, this)">30 min</button>
+            <button type="button" class="pill" onclick="setDur(60, this)">1 hr</button>
+            <button type="button" class="pill" onclick="setDur(240, this)">4 hr</button>
+            <button type="button" class="pill" onclick="setDur(480, this)">8 hr</button>
+            <button type="button" class="pill pill-manual active" onclick="setDur(null, this)">Manual ∞</button>
           </div>
           <input type="hidden" id="s-expires" name="expires_minutes" value="">
           <div class="form-hint" id="s-dur-hint">Persists until manually removed.</div>
@@ -86,7 +86,7 @@
         {% for s in active %}
         <tr id="sup-row-{{ s.id }}">
           <td><span class="badge badge-info">{{ s.target_type }}</span></td>
-          <td>{{ s.target_name or '<em>all</em>' | safe }}</td>
+          <td>{{ s.target_name or 'all' }}</td>
           <td>{{ s.target_detail or '–' }}</td>
           <td>{{ s.reason }}</td>
           <td>{{ s.suppressed_by }}</td>