proxy,ui-svelte: add request/response capturing (#508)

Add saving request and response headers and bodies that go through
llama-swap in memory.

- captureBuffer added to configuration. Captures are enabled by default.
- 5MB of memory is allocated for req/response captures in a ring buffer.
Setting captureBuffer to 0 will disable captures.
- UI elements to view captured data added to Activity page. Includes
some
QOL features like json formatting and recombining SSE chat streams
- capture saving is done at the byte level and has minimal impact on
llama-swap performance

Fixes #464 
Ref #503

ui-svelte/package-lock.json

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       "dev": true,
       "license": "MIT",
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@@ -1307,6 +1308,7 @@
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       "dev": true,
       "license": "MIT",
+      "peer": true,
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@@ -1439,6 +1441,7 @@
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       "license": "MIT",
+      "peer": true,
       "bin": {
         "acorn": "bin/acorn"
       },
@@ -3449,6 +3452,7 @@
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       "dev": true,
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@types/estree": "1.0.8"
       },
@@ -3561,6 +3565,7 @@
       "resolved": "https://registry.npmjs.org/svelte/-/svelte-5.48.5.tgz",
       "integrity": "sha512-NB3o70OxfmnE5UPyLr8uH3IV02Q43qJVAuWigYmsSOYsS0s/rHxP0TF81blG0onF/xkhNvZw4G8NfzIX+By5ZQ==",
       "license": "MIT",
+      "peer": true,
       "dependencies": {
         "@jridgewell/remapping": "^2.3.4",
         "@jridgewell/sourcemap-codec": "^1.5.0",
@@ -3716,6 +3721,7 @@
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       "dev": true,
       "license": "Apache-2.0",
+      "peer": true,
       "bin": {
         "tsc": "bin/tsc",
         "tsserver": "bin/tsserver"
@@ -3894,6 +3900,7 @@
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       "dev": true,
       "license": "MIT",
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       "dependencies": {
         "esbuild": "^0.25.0",
         "fdir": "^6.4.4",