Add config.toml support for OIDC and server configuration

- Add toml crate dependency for TOML file parsing
- Create config module with Config struct to deserialize config.toml
- Support OIDC URLs (auth_url, token_url, redirect_url), credentials (client_id, client_secret)
- Make server host/port, database URL, and session secret configurable
- Create config.example.toml with all configuration options documented
- Update main.rs to load config.toml with fallback to environment variables
- Maintain backward compatibility with environment variable configuration

Cargo.lock

@@ -107,7 +107,7 @@ dependencies = [
  "serde",
  "serde_derive",
  "unicode-ident",
- "winnow",
+ "winnow 1.0.1",
 ]
 
 [[package]]
@@ -2154,6 +2154,15 @@ dependencies = [
  "serde_core",
 ]
 
+[[package]]
+name = "serde_spanned"
+version = "0.6.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "bf41e0cfaf7226dca15e8197172c295a782857fcb97fad1808a166870dee75a3"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "serde_urlencoded"
 version = "0.7.1"
@@ -2689,6 +2698,47 @@ dependencies = [
  "tokio",
 ]
 
+[[package]]
+name = "toml"
+version = "0.8.23"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc1beb996b9d83529a9e75c17a1686767d148d70663143c7854d8b4a09ced362"
+dependencies = [
+ "serde",
+ "serde_spanned",
+ "toml_datetime",
+ "toml_edit",
+]
+
+[[package]]
+name = "toml_datetime"
+version = "0.6.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22cddaf88f4fbc13c51aebbf5f8eceb5c7c5a9da2ac40a13519eb5b0a0e8f11c"
+dependencies = [
+ "serde",
+]
+
+[[package]]
+name = "toml_edit"
+version = "0.22.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "41fe8c660ae4257887cf66394862d21dbca4a6ddd26f04a3560410406a2f819a"
+dependencies = [
+ "indexmap",
+ "serde",
+ "serde_spanned",
+ "toml_datetime",
+ "toml_write",
+ "winnow 0.7.15",
+]
+
+[[package]]
+name = "toml_write"
+version = "0.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5d99f8c9a7727884afe522e9bd5edbfc91a3312b36a77b5fb8926e4c31a41801"
+
 [[package]]
 name = "tower"
 version = "0.5.3"
@@ -3087,6 +3137,7 @@ dependencies = [
  "sqlx",
  "thiserror 2.0.18",
  "tokio",
+ "toml",
  "tower-http",
 ]
 
@@ -3467,6 +3518,15 @@ version = "0.53.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d6bbff5f0aada427a1e5a6da5f1f98158182f26556f345ac9e04d36d0ebed650"
 
+[[package]]
+name = "winnow"
+version = "0.7.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "df79d97927682d2fd8adb29682d1140b343be4ac0f08fd68b7765d9c059d3945"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "winnow"
 version = "1.0.1"