feat(templates): complete Tera migration, remove maud

Fully migrate from compile-time maud templates to runtime Tera:
- Rewrote main.rs to use TemplateEngine and discover_sections()
- Replaced hardcoded blog/projects with generic section loop
- Added Clone derive to Frontmatter and Content
- Fixed section_type dispatch via Section struct
- Deleted src/templates.rs, removed maud dependency

Users can now add sections without code changes.

Cargo.lock

@@ -816,28 +816,6 @@ version = "0.1.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "2532096657941c2fea9c289d370a250971c689d4f143798ff67113ec042024a5"
 
-[[package]]
-name = "maud"
-version = "0.26.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "df518b75016b4289cdddffa1b01f2122f4a49802c93191f3133f6dc2472ebcaa"
-dependencies = [
- "itoa",
- "maud_macros",
-]
-
-[[package]]
-name = "maud_macros"
-version = "0.26.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fa453238ec218da0af6b11fc5978d3b5c3a45ed97b722391a2a11f3306274e18"
-dependencies = [
- "proc-macro-error",
- "proc-macro2",
- "quote",
- "syn 2.0.114",
-]
-
 [[package]]
 name = "memchr"
 version = "2.7.6"
@@ -868,7 +846,6 @@ dependencies = [
  "gray_matter",
  "katex-rs",
  "lightningcss",
- "maud",
  "mermaid-rs-renderer",
  "pulldown-cmark",
  "serde",
@@ -1163,29 +1140,6 @@ dependencies = [
  "syn 2.0.114",
 ]
 
-[[package]]
-name = "proc-macro-error"
-version = "1.0.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "da25490ff9892aab3fcf7c36f08cfb902dd3e71ca0f9f9517bea02a73a5ce38c"
-dependencies = [
- "proc-macro-error-attr",
- "proc-macro2",
- "quote",
- "version_check",
-]
-
-[[package]]
-name = "proc-macro-error-attr"
-version = "1.0.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a1be40180e52ecc98ad80b184934baf3d0d29f979574e439af5a55274b35f869"
-dependencies = [
- "proc-macro2",
- "quote",
- "version_check",
-]
-
 [[package]]
 name = "proc-macro2"
 version = "1.0.106"