refactor: 移除 Python 后端源码，全面迁移至 Rust gateway 架构

- 删除全部 Python 源码 (src/) 及 Alembic 迁移脚本，归档至 _deprecated_py_src/
- 重构 Rust gateway ai_pipeline: 拆分 planner/finalize 模块，新增 contracts/adaptation 层
- 重组 handlers 模块为 admin/public/proxy/internal/shared 子模块结构
- 新增 executor 模块，引入 Rust 原生数据库迁移 (aether-data/migrations)
- 简化 CI/Docker 构建流程，移除 base image 二级构建，统一为单一 app image
- 移除 Python 相关基础设施文件 (entrypoint.sh, gunicorn_conf.py, Dockerfile.base)

Cargo.lock

@@ -115,6 +115,8 @@ dependencies = [
  "thiserror 2.0.18",
  "tokio",
  "tokio-util",
+ "tower",
+ "tower-http",
  "tracing",
  "url",
  "uuid",
@@ -305,6 +307,18 @@ dependencies = [
  "rustversion",
 ]
 
+[[package]]
+name = "async-compression"
+version = "0.4.41"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d0f9ee0f6e02ffd7ad5816e9464499fba7b3effd01123b515c41d1697c43dad1"
+dependencies = [
+ "compression-codecs",
+ "compression-core",
+ "pin-project-lite",
+ "tokio",
+]
+
 [[package]]
 name = "async-stream"
 version = "0.3.6"
@@ -711,6 +725,23 @@ dependencies = [
  "static_assertions",
 ]
 
+[[package]]
+name = "compression-codecs"
+version = "0.4.37"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eb7b51a7d9c967fc26773061ba86150f19c50c0d65c887cb1fbe295fd16619b7"
+dependencies = [
+ "compression-core",
+ "flate2",
+ "memchr",
+]
+
+[[package]]
+name = "compression-core"
+version = "0.4.31"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "75984efb6ed102a0d42db99afb6c1948f0380d1d91808d5529916e6c08b49d8d"
+
 [[package]]
 name = "concurrent-queue"
 version = "2.5.0"
@@ -1485,6 +1516,12 @@ dependencies = [
  "pin-project-lite",
 ]
 
+[[package]]
+name = "http-range-header"
+version = "0.4.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9171a2ea8a68358193d15dd5d70c1c10a2afc3e7e4c5bc92bc9f025cebd7359c"
+
 [[package]]
 name = "httparse"
 version = "1.10.1"
@@ -2024,6 +2061,16 @@ version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6877bb514081ee2a7ff5ef9de3281f14a4dd4bceac4c09388074a6b5df8a139a"
 
+[[package]]
+name = "mime_guess"
+version = "2.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f7c44f8e672c00fe5308fa235f821cb4198414e1c77935c1ab6948d3fd78550e"
+dependencies = [
+ "mime",
+ "unicase",
+]
+
 [[package]]
 name = "minimal-lexical"
 version = "0.2.1"
@@ -3917,16 +3964,27 @@ version = "0.6.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d4e6559d53cc268e5031cd8429d05415bc4cb4aefc4aa5d6cc35fbf5b924a1f8"
 dependencies = [
+ "async-compression",
  "bitflags 2.11.0",
  "bytes",
+ "futures-core",
  "futures-util",
  "http",
  "http-body",
+ "http-body-util",
+ "http-range-header",
+ "httpdate",
  "iri-string",
+ "mime",
+ "mime_guess",
+ "percent-encoding",
  "pin-project-lite",
+ "tokio",
+ "tokio-util",
  "tower",
  "tower-layer",
  "tower-service",
+ "tracing",
 ]
 
 [[package]]
@@ -4073,6 +4131,12 @@ version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2896d95c02a80c6d6a5d6e953d479f5ddf2dfdb6a244441010e373ac0fb88971"
 
+[[package]]
+name = "unicase"
+version = "2.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dbc4bc3a9f746d862c45cb89d705aa10f187bb96c76001afab07a0d35ce60142"
+
 [[package]]
 name = "unicode-bidi"
 version = "0.3.18"