fix: add TLS support for PostgreSQL connections (#363) (#427)

All PostgreSQL connection sites hardcoded NoTls, preventing connections
to managed providers that require TLS (AWS RDS, Neon, Supabase, etc.).

- Add tokio-postgres-rustls with rustls + system root certificates
- Add SslMode enum (disable/prefer/require) via DATABASE_SSLMODE env var
- Replace NoTls at all 4 production call sites with TLS-aware pool creation
- Add SslMode::from_env() helper for lightweight CLI tools
- Log native cert loading errors and warn on empty root store

Default mode is Prefer (attempts TLS, matching most managed providers).

Co-authored-by: Claude Opus 4.6 <[email protected]>

Cargo.lock

@@ -1496,9 +1496,22 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e7c1832837b905bbfb5101e07cc24c8deddf52f93225eee6ead5f4d63d53ddcb"
 dependencies = [
  "const-oid",
+ "der_derive",
+ "flagset",
  "zeroize",
 ]
 
+[[package]]
+name = "der_derive"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8034092389675178f570469e6c3b0465d3d30b4505c294a6550db47f3c17ad18"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.117",
+]
+
 [[package]]
 name = "deranged"
 version = "0.5.8"
@@ -1887,6 +1900,12 @@ version = "0.1.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5baebc0774151f905a1a2cc41989300b1e6fbb29aff0ceffa1064fdd3088d582"
 
+[[package]]
+name = "flagset"
+version = "0.4.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b7ac824320a75a52197e8f2d787f6a38b6718bb6897a35142d749af3c0e8f4fe"
+
 [[package]]
 name = "flate2"
 version = "1.1.9"
@@ -2854,6 +2873,8 @@ dependencies = [
  "rig-core",
  "rust_decimal",
  "rust_decimal_macros",
+ "rustls",
+ "rustls-native-certs",
  "rustyline",
  "secrecy",
  "secret-service",
@@ -2870,6 +2891,7 @@ dependencies = [
  "thiserror 2.0.18",
  "tokio",
  "tokio-postgres",
+ "tokio-postgres-rustls",
  "tokio-stream",
  "tokio-test",
  "tokio-tungstenite 0.26.2",
@@ -5717,6 +5739,27 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1f3ccbac311fea05f86f61904b462b55fb3df8837a366dfc601a0161d0532f20"
 
+[[package]]
+name = "tls_codec"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0de2e01245e2bb89d6f05801c564fa27624dbd7b1846859876c7dad82e90bf6b"
+dependencies = [
+ "tls_codec_derive",
+ "zeroize",
+]
+
+[[package]]
+name = "tls_codec_derive"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2d2e76690929402faae40aebdda620a2c0e25dd6d3b9afe48867dfd95991f4bd"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.117",
+]
+
 [[package]]
 name = "tokio"
 version = "1.49.0"
@@ -5792,6 +5835,21 @@ dependencies = [
  "whoami",
 ]
 
+[[package]]
+name = "tokio-postgres-rustls"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "27d684bad428a0f2481f42241f821db42c54e2dc81d8c00db8536c506b0a0144"
+dependencies = [
+ "const-oid",
+ "ring",
+ "rustls",
+ "tokio",
+ "tokio-postgres",
+ "tokio-rustls",
+ "x509-cert",
+]
+
 [[package]]
 name = "tokio-rustls"
 version = "0.26.4"
@@ -7528,6 +7586,18 @@ dependencies = [
  "tap",
 ]
 
+[[package]]
+name = "x509-cert"
+version = "0.2.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1301e935010a701ae5f8655edc0ad17c44bad3ac5ce8c39185f75453b720ae94"
+dependencies = [
+ "const-oid",
+ "der",
+ "spki",
+ "tls_codec",
+]
+
 [[package]]
 name = "xattr"
 version = "1.6.1"
@@ -7707,6 +7777,20 @@ name = "zeroize"
 version = "1.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b97154e67e32c85465826e8bcc1c59429aaaf107c1e4a9e53c8d8ccd5eff88d0"
+dependencies = [
+ "zeroize_derive",
+]
+
+[[package]]
+name = "zeroize_derive"
+version = "1.4.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "85a5b4158499876c763cb03bc4e49185d3cccbabb15b33c627f7884f43db852e"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.117",
+]
 
 [[package]]
 name = "zerotrie"