Add per-instance mod management with client-side detection

- New mod validation engine (src/mods.rs) with constant-pool class-file
  scanning: detects server-side content (block, tileentity, command,
  worldgen) vs client-only API (gui, renderer, forge/client)
- 7 client-only mods correctly detected (AppleSkin, CraftingTweaks,
  Durability101, EnchantmentDescriptions, InventoryHUD, MouseTweaks,
  TrashSlot); 51 server-capable; 1 unknown
- Routes + templating for mod upload (jar/zip), listing, delete, rescan
- Multipart upload with 500MB limit (bypasses axum's default 2MB)
- Per-instance mod summary card on edit page
- Whitelist toggle checkbox on edit page (persisted, drives ENABLE_WHITELIST)
- Dynamic Java image tag (java8/java17/java21) based on MC version
- Class scan is informational-only; rejection based on metadata side=CLIENT
- has_modpack flag cleanup on mod delete
- Remove hx-boost from <body> (was corrupting multipart uploads)

1 files changed, 88 insertions, 0 deletions

diff --git a/templates/mods/list.html b/templates/mods/list.html
new file mode 100644
index 0000000..b8aff1f
--- /dev/null
+++ b/templates/mods/list.html
@@ -0,0 +1,88 @@
+{% extends "base.html" %}
+{% block content %}
+<div class="page-header">
+    <h1>Mods: {{ instance_name }}</h1>
+    <a href="/instances/{{ instance_id }}/edit" class="btn">&larr; Back to Instance</a>
+</div>
+
+{% if let Some(msg) = flash %}
+<div class="flash flash-{{ msg.kind }}">{{ msg.text }}</div>
+{% endif %}
+
+<div class="card" style="margin-bottom:1rem">
+    <form action="/instances/{{ instance_id }}/mods" method="post" enctype="multipart/form-data" class="form-row">
+        <input type="file" name="mod_file" accept=".jar,.zip" required style="font-size:0.85rem">
+        <button type="submit" class="btn-ok">Upload & Validate</button>
+    </form>
+    <p style="margin-top:0.5rem;font-size:0.8rem;color:var(--fg-muted)">
+        Upload <code>.jar</code> files directly or a <code>.zip</code> containing multiple <code>.jar</code> files.
+        Mods containing <strong>only</strong> client-side classes will be rejected.
+    </p>
+</div>
+
+{% if mods.is_empty() %}
+<div class="card card-muted">
+    <p>No mods installed. Upload a mod to get started.</p>
+</div>
+{% else %}
+<table class="table">
+    <thead>
+        <tr>
+            <th>Name</th>
+            <th>Filename</th>
+            <th>Side</th>
+            <th>Status</th>
+            <th>Added</th>
+            <th></th>
+        </tr>
+    </thead>
+    <tbody>
+    {% for m in mods %}
+        <tr>
+            <td>
+                {% if let Some(name) = m.display_name %}
+                    {{ name }}
+                {% else %}
+                    <em>{{ m.filename }}</em>
+                {% endif %}
+            </td>
+            <td><code>{{ m.filename }}</code></td>
+            <td>
+                <span class="tag
+                    {% if m.side == "BOTH" %}tag-ok{% endif %}
+                    {% if m.side == "SERVER" %}tag-ok{% endif %}
+                    {% if m.side == "CLIENT" %}tag-err{% endif %}
+                    {% if m.side == "UNKNOWN" %}tag{% endif %}
+                ">{{ m.side }}</span>
+            </td>
+            <td>
+                {% if !m.accepted %}
+                    <span class="status-badge status-error">Rejected</span>
+                {% else if m.side == "CLIENT" %}
+                    <span class="status-badge status-warning">Warning</span>
+                {% else %}
+                    <span class="status-badge status-running">Accepted</span>
+                {% endif %}
+                {% if let Some(reason) = m.rejection_reason %}
+                <div style="font-size:0.8rem;color:var(--err);margin-top:0.25rem">{{ reason }}</div>
+                {% endif %}
+            </td>
+            <td>{{ m.created_at }}</td>
+            <td>
+                <form action="/instances/{{ instance_id }}/mods/{{ m.id }}/delete" method="post" style="display:inline"
+                      onsubmit="return confirm('Remove this mod?')">
+                    <button type="submit" class="btn-danger btn-sm">Remove</button>
+                </form>
+            </td>
+        </tr>
+    {% endfor %}
+    </tbody>
+</table>
+{% endif %}
+
+<div style="margin-top:1rem">
+    <form action="/instances/{{ instance_id }}/mods/rescan" method="post" style="display:inline">
+        <button type="submit" class="btn">Rescan All Mods</button>
+    </form>
+</div>
+{% endblock %}