feat: add image optimization and settings page

- Add persistent disk cache for processed images
- Optimize image processing with short-circuit and quality settings
- Add WebP lossy encoding with configurable quality
- Add settings API endpoints (GET/POST /settings, cache management)
- Add database table for app configuration
- Add /settings page in backoffice for image/cache/limits config
- Add cache stats and clear functionality
- Update navigation with settings link

Cargo.lock

@@ -78,6 +78,7 @@ dependencies = [
  "utoipa",
  "utoipa-swagger-ui",
  "uuid",
+ "webp",
  "zip 2.4.2",
 ]
 
@@ -317,6 +318,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "aebf35691d1bfb0ac386a69bac2fde4dd276fb618cf8bf4f5318fe285e821bb2"
 dependencies = [
  "find-msvc-tools",
+ "jobserver",
+ "libc",
  "shlex",
 ]
 
@@ -799,6 +802,12 @@ dependencies = [
  "wasip3",
 ]
 
+[[package]]
+name = "glob"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0cc23270f6e1808e30a928bdc84dea0b9b4136a8bc82338574f23baf47bbd280"
+
 [[package]]
 name = "hashbrown"
 version = "0.15.5"
@@ -1216,6 +1225,16 @@ version = "1.0.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "92ecc6618181def0457392ccd0ee51198e065e016d1d527a7ac1b6dc7c1f09d2"
 
+[[package]]
+name = "jobserver"
+version = "0.1.34"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9afb3de4395d6b3e67a780b6de64b51c978ecf11cb9a462c66be7d4ca9039d33"
+dependencies = [
+ "getrandom 0.3.4",
+ "libc",
+]
+
 [[package]]
 name = "js-sys"
 version = "0.3.91"
@@ -1295,6 +1314,16 @@ dependencies = [
  "vcpkg",
 ]
 
+[[package]]
+name = "libwebp-sys"
+version = "0.9.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "54cd30df7c7165ce74a456e4ca9732c603e8dc5e60784558c1c6dc047f876733"
+dependencies = [
+ "cc",
+ "glob",
+]
+
 [[package]]
 name = "litemap"
 version = "0.8.1"
@@ -3153,6 +3182,16 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "webp"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c071456adef4aca59bf6a583c46b90ff5eb0b4f758fc347cea81290288f37ce1"
+dependencies = [
+ "image",
+ "libwebp-sys",
+]
+
 [[package]]
 name = "webpki-roots"
 version = "0.26.11"