feat: implement real admin authentication and password management

- Added 'users' table to database with bcrypt hashing.
- Refactored login to verify against the database.
- Implemented 'Security' section in settings to allow changing the admin password.
- Initialized system with default user 'admin' and password 'admin'.

Cargo.lock

@@ -313,6 +313,19 @@ version = "1.8.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2af50177e190e07a26ab74f8b1efbfe2ef87da2116221318cb1c2e82baf7de06"
 
+[[package]]
+name = "bcrypt"
+version = "0.15.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e65938ed058ef47d92cf8b346cc76ef48984572ade631927e9937b5ffc7662c7"
+dependencies = [
+ "base64 0.22.1",
+ "blowfish",
+ "getrandom 0.2.17",
+ "subtle",
+ "zeroize",
+]
+
 [[package]]
 name = "bit-set"
 version = "0.5.3"
@@ -352,6 +365,16 @@ dependencies = [
  "generic-array",
 ]
 
+[[package]]
+name = "blowfish"
+version = "0.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e412e2cd0f2b2d93e02543ceae7917b3c70331573df19ee046bcbc35e45e87d7"
+dependencies = [
+ "byteorder",
+ "cipher",
+]
+
 [[package]]
 name = "bstr"
 version = "1.12.1"
@@ -429,6 +452,16 @@ dependencies = [
  "windows-link",
 ]
 
+[[package]]
+name = "cipher"
+version = "0.4.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "773f3b9af64447d2ce9850330c473515014aa235e6a783b02db81ff39e4a3dad"
+dependencies = [
+ "crypto-common",
+ "inout",
+]
+
 [[package]]
 name = "colored"
 version = "3.1.1"
@@ -1428,6 +1461,15 @@ dependencies = [
  "serde_core",
 ]
 
+[[package]]
+name = "inout"
+version = "0.1.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "879f10e63c20629ecabbb64a8010319738c66a5cd0c29b02d63d272b03751d01"
+dependencies = [
+ "generic-array",
+]
+
 [[package]]
 name = "insta"
 version = "1.46.3"
@@ -1571,6 +1613,7 @@ dependencies = [
  "axum",
  "axum-extra",
  "base64 0.21.7",
+ "bcrypt",
  "chrono",
  "config",
  "dotenvy",