Port 4ducky to Rust (Axum + SQLite)

Same design, layout, URLs and features as the PHP version: browse grid,
image view with AJAX comments, BBCode, likes, uploads (file, URL and
bookmarklet), quicktagger, profile, block list, inbox, invites, Hall of
Ducks, Truhe, abuse reports and the admin tools.

- Parameterized SQL, escaped templates (askama), argon2 passwords,
  server-side sessions, CSRF tokens on every write, strict script CSP
- SSRF-safe remote image fetching, magic-byte upload checks
- Self-hosted captcha replaces reCAPTCHA v1; analytics/social widgets removed
- Vanilla JS replaces jQuery and its plugins with the same DOM behaviour
- Reverse proxy support (frontend_path, trust_proxy, secure_cookies)
- Admin CLI: admin, settings, invites

See README.md for running it and the full list of changes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/config.rs

@@ -0,0 +1,126 @@
+//! All config settings. Mirrors legacy/lib/config.php; every value has the
+//! original default and can be overridden in `config.toml`.
+
+use std::path::{Path, PathBuf};
+
+use serde::Deserialize;
+
+#[derive(Debug, Clone, Deserialize)]
+#[serde(default)]
+pub struct Config {
+    // Server
+    pub bind: String,
+    pub data_dir: PathBuf,
+    pub database: PathBuf,
+    /// Set when served over HTTPS, adds the `Secure` flag to cookies.
+    pub secure_cookies: bool,
+    /// Take the client IP from `X-Forwarded-For` (only behind a trusted reverse proxy).
+    pub trust_proxy: bool,
+
+    // Names and URLs for your installation
+    pub frontend_path: String,
+    pub site_name: String,
+    pub site_title: String,
+
+    // Spam protection
+    pub upload_lock_time: i64,
+    pub max_num_uploads: i64,
+
+    // User score
+    pub post_score: i64,
+    pub tag_score_per_char: f64,
+    pub tag_score_max: f64,
+
+    // Misc settings
+    pub users_per_page: i64,
+    pub thumbs_per_page: i64,
+    pub color_search_dev: i64,
+    pub max_random_thumbs: i64,
+    pub min_random_score: f64,
+    pub max_download: usize,
+    pub jpeg_quality: u8,
+
+    /// User ids that see the HoF/Ban admin links (was hardcoded `$user->id == "1"`).
+    pub superadmins: Vec<i64>,
+    /// User ids that see the "Unblock" link on /manage (was `id == 11 || id == 1`).
+    pub unblockers: Vec<i64>,
+
+    /// Optional iframe targets for /chat, /forum and /shop. Empty = placeholder.
+    pub chat_url: String,
+    pub forum_url: String,
+    pub shop_url: String,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Self {
+            bind: "127.0.0.1:8080".into(),
+            data_dir: "data".into(),
+            database: "data/4ducky.db".into(),
+            secure_cookies: false,
+            trust_proxy: false,
+            frontend_path: "http://www.4ducky.com/".into(),
+            site_name: "4ducky".into(),
+            site_title: "4ducky.com - fol witzik".into(),
+            upload_lock_time: 7200,
+            max_num_uploads: 50,
+            post_score: 10,
+            tag_score_per_char: 0.5,
+            tag_score_max: 20.0,
+            users_per_page: 100,
+            thumbs_per_page: 125,
+            color_search_dev: 50,
+            max_random_thumbs: 10,
+            min_random_score: 10.0,
+            max_download: 8_097_152,
+            jpeg_quality: 100,
+            superadmins: vec![1],
+            unblockers: vec![1, 11],
+            chat_url: String::new(),
+            forum_url: String::new(),
+            shop_url: String::new(),
+        }
+    }
+}
+
+impl Config {
+    pub fn load(path: &Path) -> anyhow::Result<Self> {
+        let mut cfg: Config = if path.exists() {
+            toml::from_str(&std::fs::read_to_string(path)?)?
+        } else {
+            Config::default()
+        };
+        if !cfg.frontend_path.ends_with('/') {
+            cfg.frontend_path.push('/');
+        }
+        Ok(cfg)
+    }
+
+    pub fn is_superadmin(&self, id: i64) -> bool {
+        self.superadmins.contains(&id)
+    }
+}
+
+/// Grid solver settings (`Config::$gridView`). Not configurable, the CSS depends on them.
+pub const GRID_SIZE: i64 = 64;
+pub const GRID_WIDTH: usize = 12;
+pub const BORDER_WIDTH: u32 = 2;
+
+pub struct ThumbClass {
+    pub class: &'static str,
+    pub width: usize,
+    pub height: usize,
+    pub percentage: f64,
+    pub dir: &'static str,
+}
+
+/// Definition of all Thumbnail classes, in the original order.
+pub const THUMB_CLASSES: [ThumbClass; 3] = [
+    ThumbClass { class: "b2", width: 1, height: 1, percentage: 0.6, dir: "64x64" },
+    ThumbClass { class: "b1", width: 2, height: 2, percentage: 0.35, dir: "128x128" },
+    ThumbClass { class: "b0", width: 3, height: 3, percentage: 0.05, dir: "192x192" },
+];
+
+pub fn thumb_class(class: &str) -> &'static ThumbClass {
+    THUMB_CLASSES.iter().find(|c| c.class == class).unwrap_or(&THUMB_CLASSES[0])
+}