Cleanup: over-engineering pass

- merge /api/uptime + /api/version into /api/health and /api/stats
- collapse RTMP per-codec dispatch into a single CodecParser path
- dedupe STUN attribute walking (ufrag_pair / parse_xor_mapped_address)
- dedupe StreamCodec <-> str0m Codec mapping via StreamCodec::from_str0m
- dedupe bearer token extraction in WHIP handlers
- replace regex charset validation with stdlib checks
- flatten one-field wrappers (WebRtcProxyConfig, HttpServerConfig, ServerInfo)
- remove SessionCookie extractor (only fed debug logs)
- delete dead code: entity ActiveModel helpers, get_stream_session,
  WebrtcProxy::local_addr, _connected flag, commented-out blocks
- drop unused deps: futures, rand, regex, serde_json

Cargo.lock

@@ -1151,7 +1151,6 @@ checksum = "8b147ee9d1f6d097cef9ce628cd2ee62288d963e16fb287bd9286455b241382d"
 dependencies = [
  "futures-channel",
  "futures-core",
- "futures-executor",
  "futures-io",
  "futures-sink",
  "futures-task",
@@ -1202,17 +1201,6 @@ version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cecba35d7ad927e23624b22ad55235f2239cfa44fd10428eecbeba6d6a717718"
 
-[[package]]
-name = "futures-macro"
-version = "0.3.32"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e835b70203e41293343137df5c0664546da5745f82ec9b84d40be8336958447b"
-dependencies = [
- "proc-macro2",
- "quote",
- "syn 2.0.119",
-]
-
 [[package]]
 name = "futures-sink"
 version = "0.3.32"
@@ -1231,10 +1219,8 @@ version = "0.3.32"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "389ca41296e6190b48053de0321d02a77f32f8a5d2461dd38762c0593805c6d6"
 dependencies = [
- "futures-channel",
  "futures-core",
  "futures-io",
- "futures-macro",
  "futures-sink",
  "futures-task",
  "memchr",
@@ -2916,16 +2902,12 @@ dependencies = [
  "chrono",
  "dashmap",
  "entity",
- "futures",
  "migration",
  "opus",
- "rand 0.10.2",
- "regex",
  "rml_rtmp",
  "rubato",
  "sea-orm",
  "serde",
- "serde_json",
  "str0m",
  "symphonia",
  "sysinfo",