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, 1 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 828d45d..c0751fd 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -5,6 +5,7 @@ edition = "2024"
 
 [dependencies]
 axum = { version = "0.8.9", features = ["macros", "multipart"] }
+multer = "3.1.0"
 tokio = { version = "1.52.3", features = ["full"] }
 askama = "0.16"
 rusqlite = { version = "0.40.1", features = ["bundled"] }