add README, CC0 license, and button icon alignment fix

- Comprehensive README with full feature docs, settings reference,
  keyboard shortcuts, data storage layout, and build instructions
- CC0 1.0 Universal public domain dedication
- Fix button icon/text vertical alignment (leading-none + svg translate)
- Lock Cargo dependencies

src-tauri/Cargo.lock

@@ -1929,6 +1929,18 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c41e0c4fef86961ac6d6f8a82609f55f31b05e4fce149ac5710e439df7619ba4"
 
+[[package]]
+name = "mac-notification-sys"
+version = "0.6.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "65fd3f75411f4725061682ed91f131946e912859d0044d39c4ec0aac818d7621"
+dependencies = [
+ "cc",
+ "objc2",
+ "objc2-foundation",
+ "time",
+]
+
 [[package]]
 name = "markup5ever"
 version = "0.14.1"
@@ -2065,6 +2077,20 @@ version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "72ef4a56884ca558e5ddb05a1d1e7e1bfd9a68d9ed024c21704cc98872dae1bb"
 
+[[package]]
+name = "notify-rust"
+version = "4.12.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "21af20a1b50be5ac5861f74af1a863da53a11c38684d9818d82f1c42f7fdc6c2"
+dependencies = [
+ "futures-lite",
+ "log",
+ "mac-notification-sys",
+ "serde",
+ "tauri-winrt-notification",
+ "zbus",
+]
+
 [[package]]
 name = "num-conv"
 version = "0.2.0"
@@ -2342,6 +2368,7 @@ dependencies = [
  "tauri-build",
  "tauri-plugin-dialog",
  "tauri-plugin-fs",
+ "tauri-plugin-notification",
  "tauri-plugin-opener",
  "tauri-plugin-shell",
 ]
@@ -2609,7 +2636,7 @@ checksum = "740ebea15c5d1428f910cd1a5f52cebf8d25006245ed8ade92702f4943d91e07"
 dependencies = [
  "base64 0.22.1",
  "indexmap 2.13.0",
- "quick-xml",
+ "quick-xml 0.38.4",
  "serde",
  "time",
 ]
@@ -2749,6 +2776,15 @@ dependencies = [
  "unicode-ident",
 ]
 
+[[package]]
+name = "quick-xml"
+version = "0.37.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "331e97a1af0bf59823e6eadffe373d7b27f485be8748f71471c662c1f269b7fb"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "quick-xml"
 version = "0.38.4"
@@ -2798,6 +2834,16 @@ dependencies = [
  "rand_core 0.6.4",
 ]
 
+[[package]]
+name = "rand"
+version = "0.9.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6db2770f06117d490610c7488547d543617b21bfa07796d7a12f6f1bd53850d1"
+dependencies = [
+ "rand_chacha 0.9.0",
+ "rand_core 0.9.5",
+]
+
 [[package]]
 name = "rand_chacha"
 version = "0.2.2"
@@ -2818,6 +2864,16 @@ dependencies = [
  "rand_core 0.6.4",
 ]
 
+[[package]]
+name = "rand_chacha"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d3022b5f1df60f26e1ffddd6c66e8aa15de382ae63b3a0c1bfc0e4d3e3f325cb"
+dependencies = [
+ "ppv-lite86",
+ "rand_core 0.9.5",
+]
+
 [[package]]
 name = "rand_core"
 version = "0.5.1"
@@ -2836,6 +2892,15 @@ dependencies = [
  "getrandom 0.2.17",
 ]
 
+[[package]]
+name = "rand_core"
+version = "0.9.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "76afc826de14238e6e8c374ddcc1fa19e374fd8dd986b0d2af0d02377261d83c"
+dependencies = [
+ "getrandom 0.3.4",
+]
+
 [[package]]
 name = "rand_hc"
 version = "0.2.0"
@@ -3745,6 +3810,25 @@ dependencies = [
  "url",
 ]
 
+[[package]]
+name = "tauri-plugin-notification"
+version = "2.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "01fc2c5ff41105bd1f7242d8201fdf3efd70749b82fa013a17f2126357d194cc"
+dependencies = [
+ "log",
+ "notify-rust",
+ "rand 0.9.2",
+ "serde",
+ "serde_json",
+ "serde_repr",
+ "tauri",
+ "tauri-plugin",
+ "thiserror 2.0.18",
+ "time",
+ "url",
+]
+
 [[package]]
 name = "tauri-plugin-opener"
 version = "2.5.3"
@@ -3889,6 +3973,18 @@ dependencies = [
  "toml 0.9.12+spec-1.1.0",
 ]
 
+[[package]]
+name = "tauri-winrt-notification"
+version = "0.7.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b1e66e07de489fe43a46678dd0b8df65e0c973909df1b60ba33874e297ba9b9"
+dependencies = [
+ "quick-xml 0.37.5",
+ "thiserror 2.0.18",
+ "windows",
+ "windows-version",
+]
+
 [[package]]
 name = "tempfile"
 version = "3.25.0"