feat: driver rename, driver icons, web image + driver search

Driver rename and icons: `Driver.display_name` plus a `DriverIcon` table, both
global/shared like the `Driver` row they hang off, so a rename or an icon is
what every Owner sees. The rename/icon dialog keeps its forms as siblings
(nested forms are invalid HTML) and the icon routes return an `hx-swap-oob`
thumbnail refresh rather than re-rendering the table, which would tear the open
`<dialog>` out of the DOM.

Web image picker: `GET /web/images` renders a pickable grid for a printer or a
driver icon, with the search term prefilled from the entity name and editable.
Picking one downloads it server-side and normalizes it.

Driver download search: `GET /web/drivers` searches for a vendor-wide driver
(the term is rewritten into the vendor's real product name for 15 brands) or for
the exact model as typed. Links only — nothing is downloaded, and the fragment
says the results are unvetted.

Icon uploads no longer reject off-size or non-PNG files: `normalize_icon()`
letterboxes any decodable raster into a 256x256 PNG. An already-exact 256x256
PNG is returned byte-identical, because icon storage is content-addressed and
re-encoding would move the file on every save.

`fetch_image()` makes the request from the server, so `assert_fetchable()`
refuses any URL resolving to a private, loopback, or link-local address, and
re-runs on every redirect. ImpTune sits on the same LAN as the printers it
configures; an unguarded fetcher would be a port scanner for anyone who can
reach the UI.

DuckDuckGo is scraped, not called through an API — no key needed, but fragile,
so both search functions swallow parse failures and return [] instead of 500ing
a page. `WEB_SEARCH=false` disables every outbound request and hides the
controls, for air-gapped installs.

Also: one shared `Jinja2Templates` in `templating.py` instead of five per-router
instances, so a template global is declared once; `_add_missing_columns()` in
`database.py` adds new nullable columns to a pre-existing table, which
`create_tables(safe=True)` skips; `db_env` in test_db.py now closes its
connection on teardown, or the next test's ORM writes land in the previous
test's DB file.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

imptune/templates/partials/driver_list.html

@@ -30,17 +30,34 @@
             <th class="col-arch" x-data x-text="$store.i18n.t('architecture')">Architecture</th>
             <th class="col-used" x-data x-text="$store.i18n.t('th_used_by')">Used by</th>
             <th class="col-added" x-data x-text="$store.i18n.t('uploaded_at')">Added</th>
+            <th class="col-actions"><span x-data x-text="$store.i18n.t('th_actions')">Actions</span></th>
           </tr>
         </thead>
         <tbody>
           {% for item in driver_data %}
           <tr>
             <td>
-              <span class="cell-name mono">{{ item.driver.original_filename }}</span>
-              <span class="cell-sub">
-                {% if item.driver.size_bytes >= 1048576 %}{{ (item.driver.size_bytes / 1048576) | round(1) }} MB{% elif item.driver.size_bytes >= 1024 %}{{ (item.driver.size_bytes / 1024) | round(0) | int }} KB{% else %}{{ item.driver.size_bytes }} B{% endif %}
-                {% if item.driver.inf_filename %} &middot; {{ item.driver.inf_filename }}{% endif %}
-              </span>
+              <div class="cell-with-thumb">
+                {# Placeholder span keeps the id addressable so an icon saved in
+                   the dialog can be swapped in out of band. #}
+                <span id="driver-thumb-{{ item.driver.id }}" class="driver-thumb">
+                  {% if item.has_icon %}
+                  <img src="/drivers/{{ item.driver.id }}/icon" width="24" height="24" alt="">
+                  {% endif %}
+                </span>
+                <span>
+                  {% if item.driver.display_name %}
+                  <span class="cell-name">{{ item.driver.display_name }}</span>
+                  <span class="cell-sub mono">{{ item.driver.original_filename }}</span>
+                  {% else %}
+                  <span class="cell-name mono">{{ item.driver.original_filename }}</span>
+                  {% endif %}
+                  <span class="cell-sub">
+                    {% if item.driver.size_bytes >= 1048576 %}{{ (item.driver.size_bytes / 1048576) | round(1) }} MB{% elif item.driver.size_bytes >= 1024 %}{{ (item.driver.size_bytes / 1024) | round(0) | int }} KB{% else %}{{ item.driver.size_bytes }} B{% endif %}
+                    {% if item.driver.inf_filename %} &middot; {{ item.driver.inf_filename }}{% endif %}
+                  </span>
+                </span>
+              </div>
             </td>
             <td>
               {% if item.names %}
@@ -77,6 +94,9 @@
               <span class="badge ok">{{ ico.i('check', 12) }}new</span>
               {% endif %}
             </td>
+            <td class="actions col-actions">
+              {% include "partials/driver_edit_modal.html" %}
+            </td>
           </tr>
           {% endfor %}
         </tbody>