refactor: reorganize Rust codebase into modular handlers and database layers

- Split monolithic src/db.rs (1122 lines) into domain modules: projects, tags, settings
- Extract API handlers from main.rs into separate handler modules by domain
- Add proxy module for ISR/SSR coordination with Bun process
- Introduce AppState for shared application context
- Add utility functions for asset serving and request classification
- Remove obsolete middleware/auth.rs in favor of session checks in handlers

src/db/settings.rs

@@ -0,0 +1,220 @@
+use serde::{Deserialize, Serialize};
+use sqlx::PgPool;
+use time::OffsetDateTime;
+use uuid::Uuid;
+
+// Site settings models
+
+#[derive(Debug, Clone, sqlx::FromRow)]
+pub struct DbSiteIdentity {
+    pub id: i32,
+    pub display_name: String,
+    pub occupation: String,
+    pub bio: String,
+    pub site_title: String,
+    pub created_at: OffsetDateTime,
+    pub updated_at: OffsetDateTime,
+}
+
+#[derive(Debug, Clone, sqlx::FromRow)]
+pub struct DbSocialLink {
+    pub id: Uuid,
+    pub platform: String,
+    pub label: String,
+    pub value: String,
+    pub icon: String,
+    pub visible: bool,
+    pub display_order: i32,
+    pub created_at: OffsetDateTime,
+    pub updated_at: OffsetDateTime,
+}
+
+// API response types
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ApiSiteIdentity {
+    #[serde(rename = "displayName")]
+    pub display_name: String,
+    pub occupation: String,
+    pub bio: String,
+    #[serde(rename = "siteTitle")]
+    pub site_title: String,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ApiSocialLink {
+    pub id: String,
+    pub platform: String,
+    pub label: String,
+    pub value: String,
+    pub icon: String,
+    pub visible: bool,
+    #[serde(rename = "displayOrder")]
+    pub display_order: i32,
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ApiSiteSettings {
+    pub identity: ApiSiteIdentity,
+    #[serde(rename = "socialLinks")]
+    pub social_links: Vec<ApiSocialLink>,
+}
+
+// Request types for updates
+#[derive(Debug, Deserialize)]
+pub struct UpdateSiteIdentityRequest {
+    #[serde(rename = "displayName")]
+    pub display_name: String,
+    pub occupation: String,
+    pub bio: String,
+    #[serde(rename = "siteTitle")]
+    pub site_title: String,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct UpdateSocialLinkRequest {
+    pub id: String,
+    pub platform: String,
+    pub label: String,
+    pub value: String,
+    pub icon: String,
+    pub visible: bool,
+    #[serde(rename = "displayOrder")]
+    pub display_order: i32,
+}
+
+#[derive(Debug, Deserialize)]
+pub struct UpdateSiteSettingsRequest {
+    pub identity: UpdateSiteIdentityRequest,
+    #[serde(rename = "socialLinks")]
+    pub social_links: Vec<UpdateSocialLinkRequest>,
+}
+
+// Conversion implementations
+impl DbSiteIdentity {
+    pub fn to_api(&self) -> ApiSiteIdentity {
+        ApiSiteIdentity {
+            display_name: self.display_name.clone(),
+            occupation: self.occupation.clone(),
+            bio: self.bio.clone(),
+            site_title: self.site_title.clone(),
+        }
+    }
+}
+
+impl DbSocialLink {
+    pub fn to_api(&self) -> ApiSocialLink {
+        ApiSocialLink {
+            id: self.id.to_string(),
+            platform: self.platform.clone(),
+            label: self.label.clone(),
+            value: self.value.clone(),
+            icon: self.icon.clone(),
+            visible: self.visible,
+            display_order: self.display_order,
+        }
+    }
+}
+
+// Query functions
+pub async fn get_site_settings(pool: &PgPool) -> Result<ApiSiteSettings, sqlx::Error> {
+    // Get identity (single row)
+    let identity = sqlx::query_as!(
+        DbSiteIdentity,
+        r#"
+        SELECT id, display_name, occupation, bio, site_title, created_at, updated_at
+        FROM site_identity
+        WHERE id = 1
+        "#
+    )
+    .fetch_one(pool)
+    .await?;
+
+    // Get social links (ordered)
+    let social_links = sqlx::query_as!(
+        DbSocialLink,
+        r#"
+        SELECT id, platform, label, value, icon, visible, display_order, created_at, updated_at
+        FROM social_links
+        ORDER BY display_order ASC
+        "#
+    )
+    .fetch_all(pool)
+    .await?;
+
+    Ok(ApiSiteSettings {
+        identity: identity.to_api(),
+        social_links: social_links.into_iter().map(|sl| sl.to_api()).collect(),
+    })
+}
+
+pub async fn update_site_identity(
+    pool: &PgPool,
+    req: &UpdateSiteIdentityRequest,
+) -> Result<DbSiteIdentity, sqlx::Error> {
+    sqlx::query_as!(
+        DbSiteIdentity,
+        r#"
+        UPDATE site_identity
+        SET display_name = $1, occupation = $2, bio = $3, site_title = $4
+        WHERE id = 1
+        RETURNING id, display_name, occupation, bio, site_title, created_at, updated_at
+        "#,
+        req.display_name,
+        req.occupation,
+        req.bio,
+        req.site_title
+    )
+    .fetch_one(pool)
+    .await
+}
+
+pub async fn update_social_link(
+    pool: &PgPool,
+    link_id: Uuid,
+    req: &UpdateSocialLinkRequest,
+) -> Result<DbSocialLink, sqlx::Error> {
+    sqlx::query_as!(
+        DbSocialLink,
+        r#"
+        UPDATE social_links
+        SET platform = $2, label = $3, value = $4, icon = $5, visible = $6, display_order = $7
+        WHERE id = $1
+        RETURNING id, platform, label, value, icon, visible, display_order, created_at, updated_at
+        "#,
+        link_id,
+        req.platform,
+        req.label,
+        req.value,
+        req.icon,
+        req.visible,
+        req.display_order
+    )
+    .fetch_one(pool)
+    .await
+}
+
+pub async fn update_site_settings(
+    pool: &PgPool,
+    req: &UpdateSiteSettingsRequest,
+) -> Result<ApiSiteSettings, sqlx::Error> {
+    // Update identity
+    let identity = update_site_identity(pool, &req.identity).await?;
+
+    // Update each social link
+    let mut updated_links = Vec::new();
+    for link_req in &req.social_links {
+        let link_id = Uuid::parse_str(&link_req.id).map_err(|_| {
+            sqlx::Error::Decode(Box::new(std::io::Error::new(
+                std::io::ErrorKind::InvalidData,
+                "Invalid UUID format",
+            )))
+        })?;
+        let link = update_social_link(pool, link_id, link_req).await?;
+        updated_links.push(link);
+    }
+
+    Ok(ApiSiteSettings {
+        identity: identity.to_api(),
+        social_links: updated_links.into_iter().map(|sl| sl.to_api()).collect(),
+    })
+}