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/base.html

@@ -22,6 +22,10 @@
            class="nav-link {% if request.endpoint == 'links_page' %}active{% endif %}">
           Link Debug
         </a>
+        <a href="{{ url_for('inspector') }}"
+           class="nav-link {% if request.endpoint == 'inspector' %}active{% endif %}">
+          Inspector
+        </a>
         <a href="{{ url_for('suppressions_page') }}"
            class="nav-link {% if request.endpoint == 'suppressions_page' %}active{% endif %}">
           Suppressions